There are only two things that bothers me with C2 right now, from otherwise being the front runner is this game maker market. (I'm not biased towards any app, i just call them as i see them)
1.Quantity over quality. He has so much on his plate, that the direction of the development seems to be implement rough new features, to later give them more substance. I have different view on this philosophy, which is exhaust ALL areas in a feature before moving on. I know Ashley is playing the catch up game with its competitors, but just saying. (I'm probably a little bitter because i am not a programmer, so i rely on program aid like features, such as behaviors)
2.Wasting time on janky phone wrappers (or whatever you call them). If your going to try to get something on other platforms, do it the proper way by working on native builds. Doesn't matter how long it takes, but don't skimp to just have something in the program. Yeah, not a fan of phonegap/appmobi
I'm not loyal or a kiss ass, so don't take it the wrong way. Just my two cents.
As for Stencyl.... about the ugliest UI I have seen, next to Game Maker. It's recent addition of the event driven system seems to be less likable then the visual event driven style system in apps like Construct and Multi Media Fusion. The always connected to the internet deal is a minus, plus the yearly fee for the IOS export option. Those two are big problems for me as a consumer, so i dunno about that strategy.
Those are my cons for both.