I have a Dimension 8400 and i must say that it has rocked since i got it.
I do heavy media. I do gaming. I cant do Crysis but i can do UT3 and many other games with no issues.
Of course the only thing still Dell in my PC is the mobo and CPU. Everything else has been switched out.
It all depends on the person. I never had a issue with any of my Dell's. Even may laptop runs great. If you know a bit about PC's then you can get a Dell and make it work for you.