Yo, So I just bought this game today.. haven't yet played it but needed to get a thread up as I know a few of you are interested in getting it too.
Check gamespot's review:
http://www.youtube.com/watch?v=J4oJWUJpbLY
What made the first one such a joy to play was that it took a simple and fun approach of gaming. Great interaction with mutiplayer, and the best feature is that pretty much anyone can pick up a controller and be good at it. And not to mention creative!
In the sequel, from the sources I've gathered, it expands the possibilites of what the original didn't have! Improvements to different mechanics, camera shots, game modes, and powerups just to mention a few. Niv has also rated it highly, and has been playing it ever since he bought it..
Not sure when i'll get to play as it's my birthday tomorrow and will be busy, but once I get a good grip on things I'll post more info..