The best way to see the features of iPhone 3.0 is through the magic of video.
The biggest point to get out of this video is that the copy part of copy and paste works fine, but the paste part is tricky. It's not incredibly clear (right now, in the beta) where you should double tap to enable it. It seems like you need to be doing this inside existing text. The phone refused to paste into a blank spot below actual text. You'll see what I mean when you watch the video.
Other than that, the beta is pretty sluggish overall. That comes off most inside the iPod app, but it shows up as random stalls and hangs in apps all over the place.
Oh and if you like the music, buy the CD!. They're The Lonely Island, the guys behind the SNL digital shorts and the movie Hot Rod.