They tried too hard to be "not Smash Bros." and the mechanics suffered. There is no damage. Basic attacks only build up a special meter, and only these special attacks can kill opponents. It's not too bad in a 4 player brawl, but once you are down to 2 people it becomes very tedious.
This always confused me. They shamelessly copied motion controls from Nintendo, so why not shamelessly copy Smash Bros. instead of making this ridiculous gimmick? If they'd just made it "Smash Bros., except with Sony characters" then it probably would've done fairly well.
That's another thing, though, the roster just had a bunch of 3rd party characters. I guess Sony doesn't have enough confidence in their own IPs to push them. I think that'd be a lot more welcomed by Sony fans, personally, but ...
I am currently sigless.