Xbox Germany product manager Boris Schneider-Johne has claimed that newer Xbox 360 games won't gain much load-time benefit installing them to the console's hard drive as they've already been "optimised."
"This is optional, you don't have to do it. But if I do it, these games will load faster because a DVD-drive with seek operation does have load times every now and then. There are prominent examples, for instance: Project Gotham Racing 3, one of the first games for the Xbox 360. There the load times have been very long; those are going to get reduced immensely.
Recent games are already optimized; there the gain is relatively small."
The option to install games to 360's drive will be included in the New Xbox Experience dashboard update, rumoured to be launching in November.
Loading times aside, installing games to the drive does definitely mean you don't have to listen to your console's disc drive trying to lift off. Which will be nice.