Picked this back up for a bit tonight - City Escape and Rooftop Run are pretty amazing for both characters. The first 3 levels all had a bit of issues on both ends where there were just too many "pause, jump, miss the jump, try again" moments (particular new sonic levels) but these two were really well designed and exhilarating.
Challenges are a bit of a pain though, especially losing a lead in the races because you get trapped in a really shitty spot and keep missing a jump by falling through a floor or w/e. The 360 version has some framerate issues and things like that. Game is fairly dope otherwise, the story is too cute.
You'll get used to it with practice. I wouldn't try the races until you know the level design enough to speed through AND take the upper paths rather than the lower ones (but even if you take the lower paths, the doppelganger is pretty stupid, and you can get the lead anyway). Staying on the upper paths makes the races much easier. The doppelganger races aren't really the hardest challenges. Just wait until you get to the Modern Vector one for Rooftop Run. That one is awful!
If you lose your lead in a doppelganger race and you've hit a checkpoint when you were in the lead, you could always die to go back to the checkpoint to try to maintain your lead.
I'd try to do the challenges that would net skills first, though. For easier times while you're playing through the acts, remember you can equip skills to stop on a dime, get a shield, or increase your boost gauge for S-ranking.
Buuuuut you sound like you're almost done anyway. :lol
