Conceptually it does seem like a bit of a 'rip-off' but providing Sony haven't just purloined the gameplay wholesale and the game isn't garbage, I don't see an issue. I'm personally only mildly interested in buying it at the moment but if post-release impressions are good and it has solid online play, I'll probably pick it up.
I love Nintendo games (for the most part), and I love PlayStation games (again, for the most part). I'm excited for PBR, and I'm excited for a new Smash whenever it's officially announced.
As a PBR beta tester, I can say the game is a LOT of fun, and very different from Smash.