This was an extraordinary computer, and I've owned PCs, Suns, and Linux machines (this was my first Mac though). It's silent in operation, it has a ton of superb and well-integrated software, and it's really well supported and it can do things PCs cannot do, or cannot do well. I bought mine from the Apple Store, I am not sure what is gained by going through Amazon.
Quietness: This thing is silent. I upgraded to the SSD, which I suggest everyone do, and I cannot hear it at all, except once in a while when the fans come on (only Flash can do that). Even then, it's much quieter than my old Dell, which was twice as expensive and had that constant whine of cheap fans that's signals a PC like buzzing signals the housefly.
Power: This has a great Unix underneath, that is easy to access via Terminal and emacs. I had to suffer for years with Cygwin on the PC (Windows pathetic attempt to copy Unix - the world's worst Unix, constantly crashing etc., bugs galore). I prefer this Unix to Linux on the client side simply because all the polish is there - I can access really good sound cards, sequencers, video editors, and so on, without spending all my time researching drivers. Linux of course is excellent on the server side, but for client-side work, I found the Mac more pleasant.
Persistence: This is so quiet and so reliable that I really never, or almost never, have to shut down my apps. I only very rarely even hard boot the machine. That lets me just keep things up indefinitely - I have an emacs that's been up for a week, running stuff. It's really hard to explain this to a PC person, but to have the same app just up for weeks and weeks while you hone it and work on it, it's very productive.
Support: With Dell, when I had a problem, even after paying for support, they would invariably blame some third-party software vendor (e.g. Cyberlink) who in turn would blame the hardware, or just tell me to live with it (e.g. noisy fans). With Apple, the problems don't arise in the first place, or they are solved.
Usefulness: You just get more stuff done with this. The software just works better.
Cheap: There is so much free software that comes with this that you just can't get on a PC or would be really expensive. Sequencers, video editors. Even Preview would cost $200 to get on a PC (I know, I paid that to get Acrobat Standard, but Preview already has the same functionality). With Windows, it was so hit-or-miss whether anything you bought or downloaded would work at all, or would be a Trojan or some buggy piece of junk.With the Mac I get all kinds of software tools that would cost a fortune on the PC - the whole XCode suite is basically free, something comparable for Windows is four figures.
Sound: the sound on this is better than my Dell's even with a higher-end sound card.
No Junk! What's on there, works, in general. And it's there for a reason.
One example of the "No Junk" policy helped me.
My (much more expensive) Dell had a Blu-Ray player. Sounds great, doesn't it - and you can't get one for a Mac. But this was a typical Dell/Windows/PC world Blu-Ray player: in other words, junk. It was incredibly noisy, especially with the even noiser PC on. The software Dell shipped was even junkier, "Cyberlink PowerDVD", just, utter, complete junk. The Dell/Cyberlink so-called "Blu-ray" player not only lacked a step-frame feature, and only ever could play about half of Blu-Rays at all, but the whole thing stopped working a year after I bought it! Apparently some Cyberlink "upgrade" ruined it. (And dealing with PC software vendors --- the hours of wasted time, the constant demands to reinstall and reboot everything no matter what, their inevitable conclusion that the problem lies with some other vendor's product---I do not miss that, I can tell you)
On my Mac, there is no Blu-Ray player, true. So, just spend $100 on a separate Blu-Ray player. I did this, it works way better and more reliably than the PC blu-ray ever did. And the Mac is so quiet, I don't even have to turn it off to watch a Blu-Ray. It's just an example of how on *paper*, some PC feature sounds great; but in *reality*, Apple's implementation saves time because you don't have to fight the junk software and junk hardware with which typical PCs are crammed to the gills.
Downsides:
The main downside is the learning curve (for a PC user): it can take a few weeks to get the system configured how you want it and are used to where everything goes. And I don't really know a single good reference, other than a friend, experience, Apple Support, and Google. For some Windows programs, especially games, you need Parallels. Flash is worse on Mac than on the PC. Also, you want at least 4 GB.
Final hints:
You want at least 4GB RAM. I strongly recommend an SSD as well.
I personally prefer a gaming mouse+SteerMouse, and a good mechanical-touch PC keyboard, to the Magic Trackpad/Apple Keyboard that Apple sells, but I know people who prefer the TrackPad.