I've only tried out one game with the game installs, but wow it made it so much better. I tried out Lost Odyssey and the loading time was soooo much faster (as well as the system being quiet w/no dvd spinning). I have the slow loading JP version and it went much much faster than before! I played for about 2hrs and I really enjoyed playing the game again, Excellent! :D
I know some of these have been posted already but I'll list the file sizes that I have for the games I've installed so far. (I've pretty much been installing games, while I've been checking out web pages, hehe.)
DMC4 - 6.8GB
GTA4 - 6.8GB
Ninja Gaiden 2 - 6.8GB
Gears 2 - 6.7GB
Madden 09 - 6.7GB
COD4 - 6.7GB
Bioshock - 6.1GB
Infinite Undiscovery (DVD#1) - 6.0GB
Tales of Vesperia - 6.0GB
Lost Odyssey (DVD#4) - 5.7GB
I still have about 35GB of free space on my hard drive, hehe.
starcraft: "I and every PS3 fanboy alive are waiting for Versus more than FFXIII.
Me since the games were revealed, the fanboys since E3." 
Skeeuk: "playstation 3 is the ultimate in gaming acceleration"
