Harmonix has perfected the music game genre with all new instruments/modes, tremendous art style, and online play.
The instance you pop in the game, you are greeted be a good music video and once you get to the main menu, you are prompted to create your profile, band, calibrate your system, and it automatically exports your previous downloads. The game in its entirety is the Career mode. You can progress in any game mode you choose whether that be in Offline/Online quick play, Career Goals or Road challenges or anything else.
Not much can be said about the gameplay other than that its perfect. The graphics are lively and bright and pop out of the screen. It's a real light show that's for sure. Perfected framerate and character animations make for a lovely looking game.
The setlist itself is tremendous and a step above previous games. There really aren't many boring songs to play on the on-disc setlist and that's a good thing for playing with those without much DLC.
Everything is more streamlined and the main menu is at your disposable at all times including between songs for each player.
Quickplay has been slightly revamped, with it allowing all players in the band to get to choose songs. This can cause a little bit of anger to those who pick a lot of songs in the setlist that others may not to play, but also any other band member can take a song off the setlist. The Leader has the most control over the setlist so that's good.
Anything you do in quickplay is saved and progressed to your career, so you can complete career goals or challenges in quickplay. It's not longer a meaningless, pure fun mode. It has a purpose.
I cannot say much for the other instruments or the pro mode, but I've seen others play them and they say it's a blast. Can't wait to get my hands on a keyboard or real guitar to play pro mode.
All in all, you can't go wrong with this game. It is head and shoulders above Guitar Hero. Let's rock people.