Glad to hear you're open minded and receptive to improvement! It's also neat that you combined your forces to dev a game more easily! Until now, I always worked alone, like a maniac, on level design, gameplay mechanics, programming, art creation, sound, and it can get very time consuming, if you play-test 30% of the entire time-frame...
When making a platformer I think the most important thing to keep an eye out for is the margin of error of each platform's landing zone. 70% of the players will play it less-professionally than you, the devs... And especially, in the beginning of the game, until you make sure the player familiarizes with the controls, and has a firm understanding of them, especially then, in the beginning, you need to be very careful you leave them enough margin of error to learn.
Hope you guys continue to release or improve your existing games! Cheers!