I'm on the C2 boat since 2012, developed two projects on it, one really (and maybe too) big and one quite small and simple. I putted them on hold last year due to the lack of a real monetization support (at the time there was only the infamous ludei->mopub->admob thing with ridicolous fill rates and entire days of broken servers) and checked them from time to time to see how the html5 ecosystem was improving.
What puzzles me is that my apps keep loosing performance everytime I came back checking them.
There's one project (the bigger) that worked more than decently on devices really weak by today standards (with X-Walk performing even better than Ludei's Canvas+) and now, without changing anything in my code since one year, is struggling on a Nexus 5 and, despite its heavy optimization for mobile devices, even on my desktop which is quite a beast of machine.
Unfortunately this is related to the enormous mess the chromium team has done recently and, since chromium is packed in every serious exporter we have, the situation is really depressing both for desktop and mobile developers.
For example here's a link with some benchmarks runned over various chromium version.
Although the OP of the linked post is blaming D3D binding and he's talking about the WebGL renderer, I can assure that the regression curve is basically the same on Android (so there must be a different culprit than D3D) and affects also Canvas2D performance (Maybe in a minor way, and that's probably why I found today some post on this forum claiming that Canvas2D seems more consistent than WebGL on some games).
At least mobile developers have cordova/cocoonjs/canvas+ integration at the horizon... sounds strange saying this in 2015 but with the chromium suicide, cocoonjs/canvas+ is now again the state of the art of HTML5 mobile performance (but I've been burned a lot of times before, so I become ultracareful with Ludei's announcements)