It's been a while. I've sat here on my chair for a long time and thought to myself: Hey, if you want to do it, video acceleration would be really easy to integrate into Linux software: It's mostly open source and the changed would be pretty specific to that part.
Then came XvMC and it was not really convincing, because the impact was not too fast and it only worked during playback Mpeg2 AFAIK, not during transconding.
Now came NVIDIA (admittedly a couple weeks after AMD, but therefore publicly and including patches for mplayer) and finally brought out really nice and efficient video acceleration for linux.
My favorite Linux Performance News Site Phoronix checked it out and you can see quite an improvement (CPU usage with first OpenGL, then XVideo and then Nvidia's "VDPAU"(Video Decode and Presentation API).
I hope AMD and Intel will finally come out with some progress in this area, too. Next I would like to see support for encoding, e.g. in Xvid and then maybe even tasks such as gzip, bzip2 (the latter ones didn't even show multi-core support in my tests).