Tested the videos on my work machine, will try to test on my home machine (if I can remember to do so):
Dell Studio XPS
Windows Vista Business 64-bit SP2
Intel Core i7 920
6.0GB Triple-Channel DDR3 6.0GB Triple-Channel DDR3
Radeon HD 3400 Series
Tested with VLC and Media Player
Overall the MKV and AVI worked best in VLC (no discernible difference, wouldn't play in media player (surprise!))
Next best was MP4 in VLC and Media Player
WMV would only play in Media player and seemed to stutter the most
That was my experience anyway.
