Hi Ashley, that's a good point about copy, but I was originally writing the first image with source-over and got a nearly identical graph. Magnitude was different, since copy is faster than source-over, but relative magnitudes were very similar. So for that reason, I'm fairly confident that switching modes wasn't having an effect on the test.
It's also a good idea to note that all the results I've mentioned has been regarding Chrome v24.
Yeah, the Firefox results are interesting. It shows that both browsers could do a lot in optimizing canvas writes for various blend modes. It's actually source-over that firefox performs the best in, though. It's a little confusing because both source-over and destination-out are the same colour on the graph.
It should be pretty straightforward to make another test using the WebGL renderer, but I haven't done any WebGL yet (implementing drawGL in my plugin is next on my list) so I'll save that test for later.
Thanks for the info. Not being in the standard and not being supported are reasonable reasons not to include them. :)