---FOR 360 OWNERS (but applies to 360-S too_---
+ Our original 360's are freakin' loud, and that drive spinning constantly is the root cause of the noise, and of wear on the entire optical drive assembly (one cause of the red ring of death). By loading any of your existing games onto the HDD, you will ELIMINATE THE NOISE COMPLETELY. you'll still hear the whir of the cooling fans running, but that's it.
+ By loading the game, you will also speed up any wait times (next level, cut-scenes, etc.)
(Bear in mind, you have to have your original game disc in the 360/360-S in order to play...it's by design so people don't just pass around a disc for everyone to load.)
+ You can download FULL games from the Xbox Marketplace--not just "Arcade" games, but the regular, full games you would buy on a disc at the store. They don't have every game ever made available (give em' time), but it is part of the future plans for gaming and you'll see more and more of it. (Obviously with downloaded games, you do NOT need an original disc to play them).