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.
You should check out the Beta thread. There is a lot of good information and write ups about the fundamentals of the game, coming from GAF users, and not fueled by the hype train. The thread is naturally full of people that are excited for a game like this, but why should that be a bad thing? I never got why it's so prevalent to shit on people that are genuinely excited about something that is not Nintendo branded.
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.