I noticed the slowness of the hi-res videos in RC8, and decided to ignore them for now in favour of my smaller, fuller, faster set.
P4 2.8, 1GB RAM, 9800Pro, decoding via whatever got installed with the ffdshow pack someone recommended for MaLa to play the videos.
nb - Months ago now when I first tried MaLa with the videos it didn't play. I had an Xvid codec prior to installing the ffdshow pack, which worked fine with all other Xvids, and even the emumovies themselves in an external player -- just not in MaLa itself. My debugging ended when I bit the bullet and installed the codec pack, which is something I hate doing.
I wouldn't be surprised if the slowdowns are related to the relevant codec and MaLa's use of it in some way, but I have nothing to back that up.