indeed, the best things that can be done to make linux better involve the kernel and driver modules
one of the tricks of the movie and video editing linux users is to change the buffer sizes for the sound card and sometimes tweak a few others as well
after that matching your /proc settings for memory management to your RAM and HD speed/loads on system can help a bit
for the most part linux is pretty decent in most areas as is, but it still has lots of hacks in it to make it work, which is normal in any OS........sometimes you have to sacrifice something to get things to work
As an end user just choosing the right app for the job at hand makes the most difference. Eye candy and fancy GUI's dont get the job done any better than the commandline and they cost speed and resources. Choosing what you need and matching it to your hardware or load is key. Plenty of choices of apps these days, many of which are quite good, some are world classs apps without equals--->mplayer fits in that category.
Ive done tests tween windows and linux, and even recompiled linux sourcecode to run on windows, and speed wise there's rarely much of a difference. Where linux shines is under heavy loads and managing lots of intensive processes, this kind of thing brings windows to its knees, linux just slows a bit and keeps on chugging along.