Its easy to use, and i would recommend it for everyone who wants to try to develop small or big 2D games. But it takes time to get a really good result.
Its a great piece of software, that is perfect for a beginner, and even good if you already know how to code, since it reduces development time really much.
Please note, that everyone noting that C2 on Steam is instable - It's the same product & code, except how it handles to check if you bought it. It's definetely not instable, it was, but not only on Steam, and it got fixed in the meantime.
C2 also features auto-backup, Official Multiplayer (WebRTC | WiP) & there is more to come, since it's a very good maintained product by scirra. There are almost weekly updates, with fixes, improvements & additions.
If you would like to use the Steamworks API, you can't directly use it, since its written in C++ and C2 is a HTML5 Game engine. But if you have no problem with that, go ahead and buy this product, its great. (It gets reduced by 50% in Winter/Summer Sales, some times.)
And the time displayed on top of the review, is not the actual time, its only what i used in the free edition. Actual time 400+ hours (And counting).