Lap-tops are great. BUT! You can't upgrade most parts of a lap-top! The graphics-card can't be changed.
Only things you can change on a lap-top are the Hard-disk, maybe RAM and maybe the prossesor.
That's why you should allways think carefully, before buying a new lap-top. I thought about mine for a couple of weeks. And i decided, that i wanted a lap-top that could play games as well. So i paid a bit more, and got me the Vostro with GeForce 8600m GT card.
Oh, and i don't like to make a commercial here, but the Dell Vostro is a machine a can recomend to all. Other brands have lap-tops with the same specs as well, but for much higher prices!
So, try the SS08-demo, and see what it does. But don't expect to much...