I am a BETA tester for LBP2, and now the restricitons are lifted, I can tell you all about it.
There is a new game engine, so the game is a lot sharper and crisper than before, with a lot of new stuff to play with in create mode to boot.
Speaking of create, the things people have created so far is fantastic, you really can create whole games with the help of a ton of new features. This is a truely great game from what I can tell so far from the BETA, I would advise getting it ASAP, as these will fly of shelves. You can also decorate your planet and moon with all of the stickers and decouratioons you have collected, and you can keep all of the stickers and costumes you got from the first game as it interacts with you old profile
it is great to be able to talk about the BETA, so take a look at some youtube posts on it. Bear in mind it is a BETA, so the original game will probably have a lot of other stuff, and the quality of the posts will NOT reflect the release.