Oh shit, last night I was looking for when this demo was coming out. Moving this topic to the front page; Sonic 4 = controversy and we've had enough of that, so off of the front page it goes :P Opinions to be edited into here later.
EDIT: Opinions! It's tough to judge from one course, really. I can say that everything you'd expect from a mascot racing game is here. The drift handles like Mario Kart Wii's inside-drift karts: hold a drift for a bit to boost, hold longer to boost more (hold past that, though, and it seems like you slow down). With this style of drift and no moves for gaining boosts on straights, there's no way to completely obliterate the CPU players like in Mario Kart (although I'm sure racing game enthusiasts will find some other method of gaining speed to bitch about). Some jumps are automatic, even putting you into a sort of low-gravity mode, while others such as the first jump on the shortcut route -- not a spoiler, it's been in every PS3/360 vid since E3 -- are handled on your end, so you can hit them too fast and overshoot the landing. During jumps, the drift buttons change to trick buttons (also similar to Mario Kart Wii) that give speed boosts upon landing, and you can use them more than once in the air for a more powerful boost. Just be sure to be done tricking before the landing or you sacrifice the entire boost. Besides the All-Star Move for each character, items are reasonable and don't allow you to go from last to first in seconds. You also can get homing missiles in 1st place, a welcome item for when you inevitably get passed, and I've gotten mines to drop behind me in 6th, so the item balance is a bit cleaner than Mario Kart Wii although the tendency to get stronger items when trailing is there.
Am I saying that this is better than Mario Kart Wii? No, because I can't make that call yet. I like what I see, but the demo only has one course, so I don't know if what works here makes the entire game fun. If you've seen Wii gameplay of the Whale Lagoon course, that is in the PS3/360 version with the same layout, but it's locked and only the E3 Seaside Hill course (Lost Palace) is accessible in the PS3/360 demo. All in all, if you like Mario, Crash, or Diddy Kong racing games, expect more of the same, and that's not necessarily a bad thing.
EDIT 2: As if to say "fuck you, thinking that the game could be good", the demo just froze on me, leaving the controller vibrating like crazy from the drift boost I'd just gotten. That could be the fault of my Xbox 360 and not the game, but I've certainly raised my eyebrow at it.