Just beat it. Yeah Grind Square and Bantam street had some severe slowdown problems amongst other areas here and there but meh. I don't really get bothered by slowdown like this, it's not even as bad as most current gen games. The camera and controls have aged poorly, even more so than Sonic Adventure (mind you, I still think it's perfectly playable, too many people seem to make controlling SA akin to playing Bubsy 3D while blindfolded or something) but I still greatly enjoyed it. This was however after I got my bearings on the control scheme's quirks. This port is honestly really impressive to me. I praise both Sega and the team for going out of their way to retrieve the original soundtrack as well as porting it to 4+ platforms. All that couldn't have been easy. After the shit letterboxed port of a port of a port SA was to PSN, I'm nothing but happy that JSR came out the way it did, despite hiccups here and there.
I want to add I played on an OG 60 gig PS3, with little to no slowdown outside of the aforementioned levels. At least not as bad as what people here described.