According to a forum post by Epic Games VP Mark Rein, an option will be available on the PS3 version of Unreal Tournament III for installing approximately 3.5 gigs of content on the hard drive:
"Yes there is an install option which places a bunch of the commonly used content on your hard drive to speed up loading and texture streaming times a bit. It does not install everything - you still have to put the disc in the drive to run the game. The install is absolutely not essential. The game runs just fine from the Bluray and load times aren't bad but if you're going to play the game a lot, and you've got an extra 3.5Gb on your hard drive, then you might as well do the install because the few seconds you save here and there will add up over time. If you want to free up space you can delete the installed data at any time."