Addicting, fun game! Fun way to become a music star.
The production qualities of Rock Band are very polished, which immerses the player into thinking "I'm a Rock Star". When you are doing good and the crowd is pumped you can hear the crowed singing to the lyrics. The instruments provide enough difficulty that will keep you busy for a long time. At least for me, I've still got a lot of improving to do on guitar and drums. The way you can use star power to help 'save' your fellow band members is innovative too. That has helped many of us too, since pushing your abilities and skill level is the only way to progress in the World Band Tour.
When playing with your family or your buds online it's a blast - someone can play vocals, bass, guitar and drums. It's fun switching between the various instruments, and keeps it interesting. My girlfriend really likes this game, too, and has allowed us to play together. It's the one game that she's really grown to like on my 360 so that's a big plus - she won't tell me to turn it off. :-)
There are a couple things I wish could have been different in Rock Band:
1. Online World Band Tour - right now World Band Tour is local to the people who can play in your house. You can't join up with your friends online. I read just recently that the developers had planned to add it in this release, but I guess they ran out of time. I really hope it gets into a future patch.
2. The ability to create one band member tied to a xbox profile and use that band member on the different instruments. The way it's done currently you have to create a unique band member for each instrument (or let the game choose a default member).
Overall, I have to give this game a 10. When you see the credits after finishing a tour you realize how much work went into this game -- a lot! It's some of the most fun I've had. It's really making me think about beats, and about improving my guitar and drumming skills. When I'm at work I talk about this game and daydream about when I'll be able to play it next. It's really addicting fun.