Can anyone tell me if this game is of equal quality on the PS3 as on the 360? I ask because I'd rather play it on my PS3 if it's just as good as the 360 version.

I haven't heard anything negative from the PS3 versions.  I played it on 360 but some buddies of mine have it on the PS3 and they are enjoying it.

I heard the aliasing on 360 might be a bit better (as usual).  Perhaps a little bit better IQ, but it tears like a bitch.  Their was only one sequence in the game (ps3 ver.) that I noticed the framerate chug a bit, but it wasn't too bad.  All in all a great job by Vigil, kudos to them for not pulling a Bayonetta. *Angry Face*

It's actually the opposite here, the PS3 version seems to run better due to the 360 version suffering from some pretty nasty screen tearing.  (although the developers have said there is a patch coming very soon). 

Not sure about any frame rate differences, I've played the 360 version for a couple hours and it seems to run at a steady frame rate, and I've not heard any complaints about the PS3 one, so I'd assume it's a-ok.