I reckon Linux is fine for grandma (who wouldn't be setting her machine up anyway), but it's the gamers and midrange Windows used and similar who it's not ready for yet. Folks who like to click lots of installers and run the bleeding edge drivers and games, and who need the system to be forgiving of their mistakes (eg, Windows system file protection). Folks who know Windows backwards, but get frustrated by Linux being so different when they try it out. At least with Apple although things are different, they "just work".
But for the folks in Linux-land, it's hard to make software that "just works" with new stuff when you have no control over the hardware, and the hardware vendors aren't very helpful. It's also hard for the end users when some of the developers are free software bigots and won't provide easy to use installers for non-free software. Some distros have gone a way to make things easier, but I think there's a middle ground between the old-school distros and the likes of Lin- (or whatever they call themselves now).
In your particular case, there seems to be ATI and SB5.1...
ATI has accelerated 3D drivers online, but in my experience they've been hard to find, and relatively hard to install. Heck most people don't even read the instrustions for this kind of stuff, and for a non-techie it's all Greek anyway. The distros really need options for choosing non-free drivers in the X setup screens, and need vendor support to allow distro-customised distribution of them... BTW, there's also XiG which makes a fine (non-free) accelerated X server for ATI cards, and that's also an option worth checking out.
Re SB, there are EMU10K and Audigy drivers in Alsa (the 2.6 kernel sound framework) now, so if it's not working right, submit a bug report to Mandrake with what's not working and what should be different, and get it sorted. If you had problems with it, you won't be the only one.
The page loading issue was discussed in another thread, and it may be Mozilla is not set to "Enable Pipelining".
<i>Knock Knock, Neo</i>