The guitar is a cheap piece of sh!t. While it is theoretically a "real" electric guitar, it is made out of plastic and damn-near impossible to keep in tune. The gameplay using the guitar is horrible. The game itself, while not very good, is really not that bad, *if* you use a GH or RB guitar instead of the POS six-string. And no, it does not work in RB3 pro-mode.
Also, this is at least the 4th or 5th thread on this topic in the past couple months. It's been this price for quite a while now.