Having only played the 360/PS3 demo, I only have that to compare the PSV version with but it seems to be a pocket-sized conversion with few obvious compromises. The cartoon visuals looks gorgeous on the PSV and the small screen helps mask the scaled down graphics and jaggies. The framerate holds up well but a few tracks feel a bit chuggy; usually boat sections so it may be intended. The draw distance is stunning though and I didn't notice any distracting pop up so I could see everything that was coming. The drifting works perfectly once you master it and the sense of speed is OK (oddly it seems better in the super addictive time trials).
I managed to clear the first tier of the Career mode, the first Grand Prix, unlocked Amigo, levelled up Sonic to 3 and thoughly enjoyed myself. This is definitely one of the best console-to-handheld games I've played on the PSV and joins BlazBlue and Marvel vs. Capcom 3 as a demonstration of what it is capable of in the hands of talented developers. If any of the Sumo Digital developers are reading this then I'm sorry I ever doubted you. I feel so ashamed.
One annoyance though, the unlock code for the OutRun course and extra character isn't working with my game and I've triple checked that I'd entered the code correctly.
Xbox 360, PS3, PS Vita, Wii, PC (Intel Core i7-920 @ 3.8 GHz, 12 GB, 2 GB NVIDIA GeForce GTX 680 SLI, Windows 8 Pro), iPad 4