In many cases the fact that the Xbox 360 title was designed to use the DVD drive makes installing it to the hard drive actually reduce performance. While this is not true in every case it seems that big titles such as Halo 3 use the Xbox 360 utility partition on the hard drive to improve performance by caching data on this utility partition, making installing the game to the hard drive actually degrade performance.
In our informal testing in the past 24 hours or so, our results were mixed. Several titles that we tried did seem to have a very slight real improvement in performance that was noticeable by loading them on the hard drive, but in most cases the load times were about the same.
Still, the option does offer one very positive benefit, which is that you don’t have to listen to the DVD-ROM drive continue to spin during game play. Noise is one area where the hard drive loading option wins hands down.