Wanna know something awesome? There was a way to download and send user-created levels up until right before the game launched. Microsoft kinda freaked out and ordered the feature removed. Now the only way to share a level is to play as host in a multiplayer game. I don't even think it's possible to permanently send a user-created level to another player.
It's this kind of thing that's making PSN look a lot more appealing as time goes on. If they ever manage to match the important 360 features (custom soundtracks, voice chat, in-game messaging,) Microsoft will have a lot to worry about.

