As far as i'm concerned, name brand pc's tend to suck. Sure, they might be ok for a granny who wants to send and receive emails with relatives, but other than that, they're pretty gay. As has been mentioned before, the parts in them are often incompatible with "standard" bits that you would normally be able to pick up from the local "acme" computer store. I am a bit of a computer enthusiast, so building my new computer from scratch was a piece of cake. In fact, anyone with basic mechanical skills (the difficulty rating being the ability to use a screw driver) and common sense can assemble and configure a computer in about 3 hours I reckon. With most parts being plug'n'play (or as i have found out in the past, "plug'n'pray"), there's no justification for having to pay the extra hundred or so bucks for "labour" costs.
Apples have their place, especially where high-end graphics are concerned, but aren't really practical for your average bear. There's my two cents.