As far as I understand it Wii version was always gonna have multiplayer, read an interview ages ago and this is how they explained the use of the speaker so if 2 people are facing off against each other you can now hear which notes you miss and which notes your opponent misses as it comes out of your guitar.

Hmm...I'm gonna have to wait on this game if it doesn't have a reasonable offline multiplayer component...that's all Guitar Hero is to me.

Career mode multiplayer is cool...and if I can jump into the career anywhere and play a previous song...well I guess that's just like quick play...I hope so...

There is offline multiplayer, the game is in my Wii and turned on right now. I am looking at the screen. All you need is a second guitar, which should be available for the holiday. They would be silly not to.

I'd just like to add that the motion sensing in the Wii controller is a lot more accurate than the motion sensing in the SG controllers for the PS2. I've been playing for hours, completed the game on Hard and gotten to the final setlist on Expert, and I haven't missed a star power activation once. It activates the moment you want it without fail, and it doesn't get confused if you're flailing away on the strum bar while you tilt like the SG does. It makes sense, the sensors in the SG only have to detect one motion, so I'm sure they weren't designed to the same specifications as the Wii Remote. Having your star power refuse to activate when you're in the middle of a solo and about to lose is one of the most frustrating things that can happen in the game, so this is a pretty important fix.