This is only an anecdote, but I've always been an extremely slow reader, but worked hard to fully comprehend everything on the first read-through (at least for subjects that weren't extremely subtle and required lots of time to chew over). An example of this is that when I took AP U.S. History, I could just read the textbook once and ace the tests. This isn't just about having a photographic memory (which I don't have), this is also about synthesizing facts into patterns and ideas as I read. I find this very helpful and do the same thing while following whiteboard talks (except I'm apparently a much faster verbal learner, or at least I don't have trouble following talks in real time at all).

I'm not sure what direction this anecdote points in, but at the very least I'd personally be afraid to do speed-reading because it would mess up a pretty good system I already have in place.