I'v been in for a week. Nothing big.... but, they finally added the simple things people wanted. Like rating games, filtering the friends list, avatar marketplace and downloading 360 games from the games library.
I don't think that they are allowing any more sign ups. But it comes out on the 13th.. or17th of this month. Here's the link if you wanna try: http://www.xbox.com/en-US/live/2009preview.htm
you have to sign up for it, I got in the 1st wave(so hush topgun >> ), they are still releasing parts of it though.
Lol, I got in on the 2nd wave, but got the update like a week ago. I heard they were having problems updating consoles with the updates.