I'm currently testing load time differences between my standard RAID 0 and a 9GB RAM disk with the Crysis War's directory copied to it. So far the differences seem to be in the ball park of 20% (15 seconds to load from hard drive, 12 to load from RAM drive), which is pretty marginal when loading times are this low already.
The RAID 0 is my Windows disk, is kept defragmented, and reads at about 250-260 MB/s. The RAM drive reads at 5,500 MB/s. I think my results support disk not being the major limiting factor.
There did seem to be less noticeable streaming pauses while loading the game from the RAM drive however.
http://www.youtube.com/watch?v=EEtCkPcz6OY
