General purpose / casual:
anything with an Intel GPU or AMD's APU graphics (open Radeon driver or closed fglrx)
anything with an Nvidia GPU ---> run far away

Gaming:
if AMD HD7XXX series GPU and above: fglrx is the only decent driver
if AMD HD6XXX series GPU and below: open Radeon driver works well enough
if any Nvidia card: Nvidia binary driver is the only decent driver

Modeling / rendering:
Any Nvidia card + binary driver

Those who love burning battery uptime under general purpose / casual use:
anything with an Nvidia GPU + Nouveau driver

just my $0.02.