Yeah, it's been said by Ben quite well, but I feel the need to mirror his views. I don't mind getting my ass kicked when I feel like it's my own fault for playing badly. When it's something like a faulty camera that can't even display what I need to focus on properly, then it doesn't quite feel like my fault anymore.
That said, as far as Unleashed is concerned, I have more issues with the night levels personally. I can usually react quickly enough in the day stages (not always mind you, some of those spots are devilish) but the night stages had much more annoying elements to me, like the aforementioned camera. I also managed to drown while I was outside of the water a few times, which is kind of a bad thing, wouldn't you say? Stuff like that just kind of turned me off the game, and there was enough instances of defects like that for me.
At least with Sonic 4, they'd have to work extra hard to mess up the camera. It's not beyond their capabilities, mind you, but at least they have one less dimension to worry about. As long as they get the rest of the stuff working well enough that I can't pull stuff like drowning outside the water, I'll probably enjoy this more than some of the more recent outings.
I did like SatSR, though. It's controls could be wonky at times, but it certainly felt more solid overall then some of Sonic's other offerings.