1) those sprites that you're using belong to metal slug and super mario for the tiles if I'm not mistaken. that's copyright infringement.
2) the camera movement seems very rigid. Either try and reduce the delta or use a spring (or the spring formula) to dampen camera movement. it looks very jittery.
3)is there no parallax scrolling? it's really easy to implement as is pretty much a standard for 2d side scrollers.
4)the particle system engine do not seem to move relative to camera on jumping. I'm not sure if this was intended or not, but it makes the snow look fake. also, a little acceleration on the snow particles would be nice
5) I'm not familiar with objectiveC,but I'm pretty sure box2d requires some extra binding. have you done this? it's not really clear in your website.
6) the editor is pretty impressive. kudos on that Also, for other entities such as coins / soldiers / any other custom entity, where are properties such as the sprite sheets, the particle systems, the audio files etc setup? is there a separate menu for that?
7) the scripting system doesn't seem very useful. It may come in handy in a couple of situations, but I doubt if it's gonna help all the time.
6) how do you differenceiate yourself from other engines such as Unity, which have all of these features and more in their free version itself?
7) is this openGL based? are there shaders and other GLSL 2.0 features?