I played Yoshi for a while last Thursday. First surprise: it's made by Artoon! Their logo pops up at the beginning, at least. The gameplay itself is cool, and the motion sensor works extremely well. You can use it for lots of things... mainly for shifting the gravitation. If you come to a wall and can't get further, you just tilt the GB 90 degrees, making the gravitation work towards the wall so that you can walk up it. You can also make things roll (like round stones... you can roll them over piano-like tangents, making small pieces of music in the process), make ferris-wheels spin, direct cannons, direct falling things, and roll out pieces of rolled-up grass over chasms.
It's very, very pretty! Looks a lot like Yoshi's Island, and uses tons of rotation-effects. The music is a bit irritating, though. I didn't play very far... through the first world, consisting of three levels, and to the end of the second world, which has around six levels. Each level is VERY short, at least in the beginning, making it more of a puzzle-game than a platformer, since every level gives you a new way to use the sensor, and you need to master it in order to continue. Some of the levels can be cleared in a minute or so, but they get longer and more convoluted as you go. I hope the later levels will be far longer, and more like a platform-game.