You can ask 10 people and all will tell you something different.
I've had excellent luck with Dell's and HP's, bad with IBM's.
I generally build my own though. I'd stay away from Alienware and the like unless you want to pay a lot of money, if you want to pay that kind of money have someone locally build one.
If you are just going to be on the internet and a few things the cheapest you can find should work ok.