Well, if you invest the same amount of money in quality parts as you spend in a new Mac, your HW is in good condition and there shouldn't be any problems. Especially if you let your pc-savvy friend choose the parts according your budget and need. Not the neighborhood guy but the guy that really has 10+ years in the industry.
With Mac, you already paid for this service, to some extent.
With PC, you don't necessarily have to have replacement parts, it's an option. You can buy a new PC when the old one gets too slow like you have to do with the Mac. With PC, you can upgrade just some parts and move some stuff over to get an almost equally good new PC without paying the full price.
And the software... I've had numerous bad experiences with Mac's regarding shitty software. If you run something that has loads of bugs, you are inviting some odd behaviour no matter what. In both worlds. The worst one have been PS and some other lighter software that I run on Mac and when they crashed, the whole OS would crash also (OS9, haven't really used the X. Played around with X and now I feel a need to buy a 12" powerbook
). With Win2k+, I just kill the program and re-launch it. No nasty corruptions on harddrive due crash & stuff.
In the end my PC won. Same or equal software, more responsive with the same amount of money invested in hardware, more affordable upgradeability.