Alright, I'm going to make this short.
I'm buying a new computer, either a Mac or a Windows desktop that I'll build myself.
What are the advantages of buying a Mac over building a Windows computer?
I don't want to hear "It's pretty", that's subjective. Nor do I want to hear "It's more user friendly", I don't think it is nor do I need the extra help. I don't want to hear "It doesn't get viruses" either, because I'm not an idiot who gets viruses.
So, what are the advantages?
I am in the same boat as you. I have built my own Windows desktop since the early 2000's. I always got what was top of the line parts for not that much money, buying from Newegg, Amazon and online computer stores. I built my last machine 4 years ago and I am in the market for a new computer. I bought my wife an iMac 3 years ago and found it to be very intuitive. If you are buying a computer for gaming, an iMac is not what you want. iMac's are really not great high end gaming devices like you would be able to build with your own Windows PC. For me, I don't need it for gaming, since I have all three gaming consoles (PS3, XBOX 360 and Wii). Also, I injured my back pretty bad, and really don't want to build my own computer anymore. I want something good that I could have the best of both worlds, Mac and Windows together on the same machine.
When deciding on a computer, either MAC or Windows, you have to ask what you are going to use it for? You should list the positive and negatives.
Here are some positives and negatives for the iMac.
1. The iMac is compact and doesn't take up a lot of room.
2. Mac usually don't get virus, but could carry a windows virus that if you transfer back and forth to a windows computer, could infect it.
3. No registry to mess up, like in a windows machine.
4. Mac OS are usually a step ahead of Window's OS, in my opinion.
5. Can run Windows and Mac either virtually or through Bootcamp, like having two computers in one.
Negative:
1. Not easily upgradeable, except the RAM. Can't change out video, HDD very easily.
2. Not great for gaming
3.Can't play Blu Ray movies through a MAC, but can burn blu Ray data.
In the end it is up to you of what you want. If you can, go to an Apple store and try them out first, before you buy, and ask questions at the store to see if an iMac is right for you. For you, maybe the Mac Pro might be better for you, upgradeable parts, tinkering, and it is on par with any Windows PC you would build. It is more expensive, but you would have the best of both worlds
Good luck