Yea, I have it coming from GameFly so I'll get to try it out before I make a decision. I agree with the OP in that I prefer Rock Band, but I would like a rhythm game to play before it releases next month.
I think sales of this will be underwhelming and you will see alot of good deals on BF and beyond. So unless you really want to play now you can probably wait on it to drop or hit clearance next year.
EDIT: There is one other bonus that I didn't mention before. If you buy the game before Oct 5th you will get a FREE export for a bunch of GH Metallica tracks. You just need the code from the back of the GH Metallica manual and the game disc for GH WoR. The tracks will be playable in GH5, Band Hero & GH WoR.