As strange as it might sound, except for a few things, the hardware support for Linux is excellent. Often much better than for Windows. Nowadays, you only have a problem with that if it's really new. Because those drivers are generally written by supporters, not the HW manufacturers.But it won't solve the problem a Joe Sixpack who's bought a piece of hardware at PC World expecting it to work with his shiny new Dell, only to find out that there aren't a Linux drivers for it (for any one of a number of possible reasons).
Then again, many big HW manufacturers, like HP, Logitech and VIA, have excellent Linux drivers.
I think WiFi and ATi videocards are the biggest problem cases in general. The first is solved, but it takes some time to write those drivers, and the second is solely due to ATi/AMD.