technically it's still in beta...
the only difference really is in the interface. It has some easier to use features.
the cloud storage is pretty nice, integrates with Google seamlessly.
the add-on manager is a really nice feature.
I have only been using it for a few months and haven't tried any large projects with it. I do really hate that it has to run in Chrome (or another browser) but I think there is a beta web-desktop version.
also new features are coming to it... C2 is the past, C3 is the future.
C2 or C3 is still, hands down, the fastest engine to make a prototype 2D game out there. (I think anyhow)