My only concern about using 3rd party plugins is that major changes to C2 - like the forthcoming introduction of multiplayer - could break them... and Scirra are forthright in not supporting 3rd party add-ons when it comes to bug fixing. Unless I've missed something they are still not permitted on the Arcade, for example.
Scirra sell C2 as a platform that gives non-code-writers the ability to make games and I think it's an excellent tool. However, some of of the juicy and very useful game-making functions, like ad support - the ones you want after you've messed around with making a simple platform game for your mates - are not provided at all and are only indirectly supported through the SDK.
I know this thread is about ad support, so I'll limit my diatribe here... C2 is still the best tool out there for amateur / non-coders to make games, but I do wish that ad support would be formally provided.