I'd say the limit is the time you can put in learning C2's ways.
Also the limit is your imagination/knowledge as far as solving problems with C2 goes.
Apart from that and the several points previously mentioned, there is no real limitations.
You could always have a try by yourself with the free version which has some further limitations :
You can make only 4 layers / layout, use a total of "only" 100 events on your project and use only 2 WebGL shaders effect.
If you want, and to start learning how to use C2, have a look at my tutorial Asteroid clone in less than 100 events
Also, you can check the arcade
and see the games made with C2 and try to see if you find any kind of limits you would like to have clarification about.