I've noticed different thing with very fast scrolling background some time ago (with C2 r81) and yesterday I opened up that project to see how it works after exporting to awesomium.
Here's html5 version - Trench Run HTML5
Here's exe version - Trench Run.exe
Move with arrows
shoot with space (hold space for powerful shoot)
On my pc, html version is quite unplayable. Frame rate stay high, but screen is very choppy. At first i though that's the issue caused by those panels/grebbles sprites. I did spawn and delete them on runtime (almost 300 sprites on screen) to create never ending tunnel - spawn on top and destroy after leaving layout. On second attempt I placed them on layout and only move y position to wrap around the screen - doesn't help a bit. On my last attempt (current version) I've converted them to TileBG, 1 Tdb = 9 old sprites, so on screen i have only 6 tilebg's - still no improvement.
I'm not sure but pretty convinced that is caused by time delta. I could be wrong, but remember doing some test without dt and screen moves a lot smoother - but speed was different due to frame rate difference.
With exe there's no issue at all, runs very smoothly.