I bought a Frontman and kind of regret it.
The buttons are considerably more stiff than the original, so it takes more effort to play especially in higher difficulty levels. It's not terrible, but noticeable.
The frets are really high and sharp. I actually took a Dremel tool with a sanding attachment and ground the frets down just to make it not painful to play.
The neck doesn't come off the body. This can be a good or bad thing.
On the plus side, it was cheaper and while the frets were a real problem once I sanded them down the guitar is responsive and everything. It feels kind of like a Bass guitar in relation to the normal guitar that is the official controller. And it looks like a Telecaster, so that's cool.
One minor gripe, the faceplates are not nearly as convenient to change as on the official guitar. You need to unscrew 7 security bits to remove the face plate. It comes with a little screwdriver that has a storage spot where you put the remote, but still, much more complicated than the official guitar.