Great work. I won't repeat the praises others have already given though, and go straight to my comments :-)
One question i'd like to see more explicitly addressed in such surveys is, How counterfactual has the EA movement actually been?
I've only skimmed through the report, but it didn't seem like you do much to address this question. I'm much less concerned about the $333 median donation than i am about the $6.8 million total donations. That's about 20% of what GiveWell attributed directly to their research in 2014 [http://blog.givewell.org/2015/04/13/givewells-money-moved-and-web-traffic-in-2014/] (still only about half of it, if you discount Good Ventures grants).
Your table showing that GiveWell is how the largest number of EA respondents got more involved with effective altruism suggests that there might be a lot more people out there hearing about GiveWell and whatnot from other means who are essentially effective altruists, but don't know about it, or simply don't identify with the movement for some reason. Do the responses from people who have heard of effective altruism but don't identify themselves as effective altruists shed any light on why this is so?
I'm wondering whether one could run the same survey in parallel to, say, GiveWell followers and the donor bases of some EA-vetted charities, but with the questions, 'would you consider yourself an EA' replaced by, 'what factors did you take into account in choosing the charity you donate to' --- with the term 'effective altruism' tabooed, if you will.
Of course this only touches on the 'individual donations to charity' dimension of effective altruism, and i'm not sure what fraction of the total impact of the movement that should represent --- or even how to measure it.
I hope this is helpful :-)