Dells are good (though still overpriced) for people who don't use their computers - and I mean really USE their computer. I'll clarify what this means:

NOT using a computer:

chatting online
word processing
internet browsing
dvd watching
most (not hardcore) gaming
downloading (music, videos, images)
photoshopping the way 98% of the population does


REALLY using a computer:

programing that actually does something useful
math humans cannot computer in under an hour
high-end web design
professional photoshop, flash, etc
high-end gaming
media production