Saw it last night, and I'm kinda torn on how I felt about it. It did have some genuinely funny moments, but I think it would be a mistake to judge the tone of the movie on the trailers...
The trailers kinda portray it as a whacky Jack Black vehicle, but it's much more whimsical and sentimental in reality. So it's very much a Gondry film, rather than a Black one. Some lovely quirky visuals though. Very imaginative... Just don't go expecting to be laughing for 90 minutes.
Overall, it had a certain charm to it, some good laughs, but I left feeling somewhat unsatisfied. Maybe I didn't eat enough sweets.