Speed is still a large concern using C2 if you are making anything with a large computational overhead, i don't see this changing anytime soon with javascript. You need to have used CC extensively to make any fair comparisons/arguments about the capabilities, they aren't something easily seen from the surface.
I've used CC and C2 extensively and comparing them, C2 can do the vast majority of what CC can. C2 isn't as fast at event execution, but the vast majority of users won't have any problems speed wise or need the features from CC that it won't get.
For those who do want those things, though, I understand your disappointment.
You're better off using java if you want to make something serious that will also be multi-platform. A lot of people used construct to make something more than an angry birds/fruit ninja/cut the rope/generic app clone. CC and C2 as things stand are different tools for different Jobs, and although C2 does it's job more effectively than Classic, it does not, and most likely will not be able to do classics job for a long time (if ever, depending the direction scirra takes).
If you used java, you would miss out on one of the main things that makes construct two so great, its event editor.
C2 is more than capable of making something more than a generic app clone. C2 can do classic's job just fine as long as you do not need the specific features or event speed that it lacks, which again, most people don't.
shinkan - I made some event speed tests earlier in the thread. I messed up on my first attempt though, so look for my second set of tests on page 4. I also tested rendering speed earlier, and c2 wins in that department.