I know I just pushed up 1.2, but I just realized I could hook the BeforeNavigate2 event and pre-filter downloads from blocked URLs before the download even begins. This should presumably save bandwidth, and stops blocked images/scripts from even loading (avoiding that momentary flicker on the screen).
It also, in my highly unscientific tests, seems to be faster.
There is a downside. In this event, I don't know
a) the type of the thing being downloaded (image, flash, etc)
b) the hosting site
This breaks some of the specificity of our rules, though I don't think that specificity is really used. But it means that if you had:
then downloads to http://bad/, even from site "exception," would be blocked. This is counter to the defined semantics.
So I think I'm going to break the rule semantics a bit for the next release, which will be coming shortly. I have to think about this a bit more--and look at what other adblockers do--before I figure out the right approach.