I tried the Sonic Racer yesterday and I didn't like it either much.
I was kinda surprised in a good way of the intro when I saw the protagonist Vyse of Skies of Arcadia driving one of the cars. Sadly he's not a choosable character in the demo. There were plenty of unlockable characters.
As for the gameplay, it was pretty Meh. IMO it should've had a bit faster speed. The air-mode felt most solid for some reason. The fact you go between water-driving, land-driving and air-driving is just a gimmick. Why don't they just focus on one area and make that one area the best area ever? The water driving does not have the great simulation that Wave Race on the Gamecube had for example. The car driving doesn't have the same responsiveness as F-Zero GX or the newer Mario Karts. The air-mode is the only one which felt kinda solid. But that's mainly because there's not really that many racers out there which are airial racers. The air mode as mentioned felt most solid, it was pretty much of Diddy Kong Racing-caliber.
To me, the game felt kinda empty. I love the fact they base their levels of famous games. Like the second level where u are supposed to get all the boosts is based of Golden Axe. It was a pleasure to hear a remixed version of Golden Axe theme there. However, had it been a mario kart level, surely there'd been more golden axe goodies in the level. Such as the goblins which has food and potions, maybe monsters running around and perhaps even the mounts. All there to make the track easier/harder for you.
Graphicswise the game is very appealing, but that really doesn't help much when the driving just doesn't go fast enough.
All in all, it's definatly a game I won't purchase. The demo did NOT convince me. There's some great nostalgia in it, but the gameplay itself just isn't as tight as a Mario Kart. Because we all know this is really just a Diddy Kong Racing/Mario Kart clone.