I found this game to be pretty interesting and generally enjoyable, however that last level takes the skill needed in previous levels and adds a rather unappealing luck factor. The game isn't meant to be easy, but when you have to replay a certain level or checkpoint over and over again ad nauseum, the overall level of frustration starts to soar. Long story short, the wind effect - while being an interesting idea in theory - is way too cheap and monstrous when you have to rely on near perfect timing to get past obstacles.
That being said, I'm happy to report that I pushed on through to the end, and I'm glad I did. I was able to snag some in-game achievements, max out the upgrades, and earn some nifty Newgrounds medals in the process. While I may have found some of the obstacles to be somewhat over the top vicious, I found the gameplay itself to be fun, in a particularly frenetic sort of way. I even soldiered through one of the challenge levels with the fourth character to earn yet one more achievement before calling it quits.
Playing most of the levels from start to finish without having to restart a checkpoint requires an incredibly amount of luck, but fortunately there's still a chance to claim the silver (or even gold) medal even if you get bounced back once or twice. Except for the final level that is, where I can't really imagine anyone being lucky enough to walk away with a medal of any kind. The addition of four different player characters is a nice touch, but I honestly didn't end up using that many character abilities to get through the levels. The upgrades are a nice touch, but many of them are all but vital for later stages, so that would have seemed kind of unfair if it weren't ridiculously easy to accumulate coins.
Well, in conclusion I have to say good work overall. You've made a game that looks nice, and it plays like it's supposed to--even if it's a bit of a frustration fest at times. Nicely done.