This is the most fun you will ever have with three of your friends.
The first Rock Band was great. I was expecting more of the same -- not that it's a bad thing -- but I was blown away from the actual experience. I've found two things that stand out in this game.
The first thing I noticed was how precise you could adjust the timing. This helped immensely as we played the game on a DLP projector and home theater receiver, of which both sources can introduce all sorts of latency. With the ability to adjust both video and audio lag, we found the timing to be spot on.
The second thing I noticed was the improved note charts. I love playing bass on expert, and I found the note charts to be a lot more fun, challenging, and most of all satisfying than what I had experienced with the first Rock Band.
Also, I love RB2's track list. While Rock Band had a solid track list, there were only a handful of songs that we would play. In Rock Band 2, pretty much every track is a winner. There's everything from AFI to Beck to Paramore (yes, I love Paramore) to Social D to the Bosstones.
Speaking of the Mighty Mighty Bosstones (yeah, I know, most people hate ska these days, but I grew up listening to them), I was so excited to see them pop up, but very disappointed when it wasn't Dicky Barrett singing.
Rock Band 2 is a must-have game, especially if you have friends. It brings out the best in everyone. My friend Greg was absolutely positive that he could not sing so he only played guitar. We peer pressured him into singing, and as it turns out, he's actually pretty good. See? Doesn't that just make you feel all fuzzy and warm inside?
My verdict: buy this game and play it immediately. That term paper can wait.