I use it as a secondary guitar, but just because its design isn't as slick as the official RB2 guitar. Other than that, I don't see any problem with using it as a primary guitar, works fine.
I actually wrote a review on Amazon for it on there. I basically said that aside from a few minor design differences (biggest one being slightly farther apart fret buttons) and it feeling plasticky, it worked just about as fine as the official RB2 guitar. Definitely good for $13.