My impressions are ambivalent. When I had run it (C3) I felt like I was working on C2 but somehow deprecated. I saw the same options and the same workflow but sometimes I felt a little lost - for example I could not added behaviour to the object for the first time. Just a while later I pressed a right mouse button for a submenu. I had looked for a new stuff but I could not find them fast, so I think I don't need them at now.
I like the plugin idea. It could be added to C2 too
So for me this is a C2 in the browser which doesn't fit my expectations. After the test I was happy to run C2 again.
So in my opinion C2 is a good tool. So good that the new one could not beat it yet...
... and it is working slower than C2.