I will join in with this Apple/PC discussion. I think if you just want to have a computer that will not give you trouble and will just work when you want it to, absolutely go for a Mac. But if you are computer savvy, then both are excellent options for you. If you are more hardware prone, then PCs are the way to go. What I mean by this is generally, Apple software is usually more stable and have fewer bugs. Since their move to OS X you also have the flexibility of Linux. Thus if you like to program and tinker in the operating system, both Mac and PC are good choices. I suspect most of you guys will just want a working computer with no fuss, but I am a hardware tinkernut so I absolutely can't have a Mac as a desktop.
As for the software/program compatibility discussion, this line is merging very closely now. OS X is Linux based and more and more programs are written with these two in mind. Along with the switch to Intel CPUs, there might even be a future of Windows on Macs although that would defeat the whole "Macs don't have to deal with the bugs/vulnerabilities/crashabilities of Windows" argument.
Now price is another place of concern. It is now cheaper to own a Mac than before with the price drops midrange Macs. This includes the iMac desktop and iBook laptop. But if you want the best like the G5 desktop or Powerbook or Macbook Pro, prices are steep. Because Apple doesn't have direct competition, prices will always be higher than PCs. I mean 2000$ minimum for a Macbook Pro is a bit ridiculous in my opinion but Apple did recently do a free CPU upgrade for everyone who ordered one due to a shipping delay.
Now I have the same problem of choosing although not for a desktop but for a laptop which I think I will need. I was looking at Thinkpad X60s and T60s as well as the MacBook Pro and couldn't decide yet. I'm going to wait and see. So my final tip for those who are going to buy a Mac is go for the laptops. Why? 1. They will become obselete less quickly than Apple's desktops 2. Some of Apple's design advantages will be more pronounced than on their desktops 3. Customization is irrelevent since neither Mac or PC laptops are meant to be modified (a big reason why I stick with PC desktops)
I know I provided my views without much examples to back it up so hopefully I'll check back and reply to questions.