I bought a Dell about 7 years ago, and I'm still using it. It had one problem in all that time. I got the dreaded "Flashing Amber light" which is common for certain Dells from what I've read. It was caused by a dead/dying PSU, which I swapped out and all is well. Warranty and customer service are pretty crappy to be sure. I've upgraded this particular computer as far as I'm willing to go, but 7+ years of service is nothing to sneeze at.
I also have a Toshiba laptop, which I bought about 2 years ago. I don't use it as much as the desktop, but I've had no problems with it at all.
Having said all that, I agree that building your own is the way to go. I'm currently putting together a desktop for my parents (my first build), but given what I've learned so far, I'd never by pre-built again.