The Quick Version
Great looks, great functionality, an excellent all round computer. Only the price would make you want to check out the other options (like a Chromebase).
The Key Points
1. The best full function computer you can buy.
2. Excellent security.
3. Much more expensive than its competitors.
The Apple iMac is an All-in-One machine. That means that it looks like it's just a screen and surely there must be a lead coming out the back and going to the real computer? - but no! In fact with all-in-one computers all the brains are cleverly hidden away behind the screen (there is no separate box under your desk), leading to a very neat and good looking piece of kit.
The iMacs principal advantage is that it is a full function computer, meaning you can run just about anything on it. The only type of machine that is more full functional would be Windows computer, which has attracted more support from people writing software and making hardware, simply because it has a much much larger market share. However, Windows has an enormous disadvantage in terms of security. Although Mac security is not perfect, it's vastly better than Windows in this regard.
The iMacs principal disadvantage is price. The basic iMac is very roughly twice the price of an equivalent Windows All-in-One and 4 times the price of a Chromebase (and a top of the line iMac is 2 or 3 times as much as a basic iMac. You get the idea, big difference). Despite the price difference it's still worth considering because software infections on Windows (which are very common) could cost you more (in clean up costs, stolen money and lost files) than the price difference to get an iMac. The Chromebase is a fantastic bargain for most folks, but if you need some software that doesn't run on Chromebase, iMac is the best place to look.
Security on the Mac is good. Probably the only downside is people think it is invisible and that's not true of any type of computer. The reason that's a problem is people will ignore precautions that would be automatic elsewhere. Read The Security Hierarchy for more details. The short answer is Mac security is good, probably good enough for most people most of the time, just not quite as good as systems that were designed much more recently like iOS and Chrome OS. Should you worry about the difference? Probably not.
Macs don't come with automatic backups built in (unlike an iPad or iPhone, which automatically backup to iCloud unless you tell them not to). It looks like Apple are moving towards having the same sort of automatic backup to iCloud on the Macs, but it's just not quite there yet. There are pieces of the puzzle in place, but not the whole jigsaw. So although there are some iCloud functions on the Mac, you will need to take some extra steps in the meantime if your files are to be safe.
Ask in the Apple store and they will tell you to buy an Apple Time Capsule (US $277 - UK £215). Although this is a good piece of kit, I have one huge problem with it: it is a backup device that is in the same building as the computer it is backing up. That's never a good idea. I get calls from people who have had a burglary and the thief has stolen their computer and their backup drive. At least one copy of your backup needs to live somewhere else entirely to the computer.
That's where automatic online backups come in. You put some software on your computer. Pay a fee to the supplier and it will encrypt and send your files to a remote server a long way away. So if bad things happen to your computer (hard drive failure, house fire, burglar, alien abduction etc) all your files can be recovered from the remote service. One day Apple's own iCloud service will do that for you on the Mac. Until then, get www.carbonite.com. It's a great backup service, they have been around for years and I personally have recovered data from them for numerous customers. They always get the data back.
Very good. You can do almost anything on it.
This does not crop up much in the home market, but sometimes people find they have to run programs that only run on Windows. If that's your situation there is a cunning way around it on the Mac: you buy some software called Parallels (US $70 - UK £65) that will enable Windows to run inside the Mac. You need to get Windows as well (US $97 - UK £70). With that you can run any Windows software you like (although be aware that the Windows part of the machine will be just as susceptible to infections as any other Windows computer).
Even more unusual (in the home market at least) is hardware that will only run on Windows, but it does happen. For example I just saw a musician who has special hardware boards in his PC to do musical things that are beyond my non musical comprehension (but they keep him happy). He is stuck with Windows because that's the only type of computer that will talk to his boards. If you have any wacky hardware, make sure it runs on the Mac before purchasing.
None of this is normally an issue. Most folks have everything they need in a Mac. But then most folks have everything they need in a Chromebase.
But of course that's the entry level product. I can see in your eyes you really want the good one. Which would be the iMac with Retina 5k display (US $2,449 - UK £2,172). What makes this ridiculous cool is the quality of the screen. Full HD screens are great, right? You do know that the TV manufacturers have started to ship 4k screens, those have 4 times the number of dots making up the picture, more dots means high quality, more life like images. This 5k iMac has twice as many dots as a 4k screen (or 8 times as many as a full 8k). Sounds like techie nonsense that you would never care about? Go to an Apple store and have a look at one. Pay special attention to what the text looks like on a normal iMac and on the 5k. All that techie nonsense will fall away and you will say "oh, I get it, that's the best screen I have ever seen and I want one". No other manufacturer is doing anything close to that right now.
If these prices are making you wince, make sure you look at the Mac Mini, that's the cheapest way to get a Mac and definitely worth a look.
What's wrong with choosing an iMac?
Obviously price is an issue. One way of fixing that is to grab a Mac Mini instead. That's a small desktop computer that you can plug into your existing screen. It's not as tidy, but it is cheaper (ok, not as cheap as an alternative like a Chromebox, but it is cheaper than an iMac).
It might be worth checking any software or specialist hardware you want does run with the iMac, just in case it's Windows only. Although for most people this won't be an issue.
Portability might be an issue, but remember, you don't have to have one device to rule them all. You can have a nice big machine on your desk and a cute dinky one for traveling (like an iPad or a MacBook Air). Apple have done some great work to make all your files synchronize up between your different machines.
But this is all nonsense!
There's a staggering amount of misinformation and urban myth doing the rounds on the subject of home computers, often nonsense that is most definitely against your best interests. So let's prepare you for when someone "who knows about computers" comes knocking by covering the popular hogwash in advance.
I won't be able to use a Mac, it's all different!
Probably less different than you think. I changed the main screen on my desk over to Mac about a year ago because I wanted to become very familiar with all of its ins and outs (having had Windows on the main screen since the pyramids were being built, but I've always had lots of other operating systems on the other screens on my desk, still do). Most of the time I forget which operating system I am using. Right now I am typing these words into the Squarespace website on my Mac Mini, later I might be on a Windows laptop doing the same thing. It's the same experience, I will still be typing stuff into a website, regardless of what kind of computer it's on. It's also pretty much the same in Word, Excel and lots of other things. I do find lots of little things irritating about the Mac, not because they're wrong, but because they are different to what I am used to. Like the scroll wheel on the mouse going the opposite way to Windows. I switch between machines a lot now and I am never sure which way it's going to go when I scroll.
However, the irritations are worth it for the ability to climb out of the cesspit of security problems that is Windows (see Viruses and Junk Software).
Just remember, whatever type of computer you choose, it will be different to the one you are using now. Even if you have used Windows forever, the latest version of Windows will be different and it will take some getting used to.
I don't want to be a "Mac" person!
This will come as a big shock to Mac people, but Macs have an image problem. When I suggest a Mac to normal people a surprisingly large number of them complain about the arrogance, religious fervour, camping out in front of the Apple Store for 3 days, Macs can do no wrong, you know the sort of thing. Normal people don't like it and don't want to be associated with it (to be fair Apple have done well to avoid this problem with iPhones, iPads & iPods, those are objects of desire and everyone wants them).
It can take a little while to talk people down off of this and get them to the point where they just buy what is right for them. If that happens to be a Mac, get a Mac. The badge on the front does not make you a fanboy. You don't have to subscribe to their religion, it's just a computer. You will have had computers before it and you will have computers after it. Buy what's best for you and laugh at the fanboys (we all do).
Don't be shy, say what you think. The comment system below is there for anyone to ask a question or make a point. Especially don't hold back if you are a normal person just trying to make sense of it all. It's easy to get the opinions of geeks on geeky matters. Much more interesting to hear how this works out for you or what bits need more explanation. No such thing as a silly question, jump in.