Well, how about everything I've been arguing (social instability from new divisions) and Proto's "Gene pool based elitisism"?

I bet you could find dozens of sci-fi books/stories that delve into possible dystopic scenarios.

Like I said before, we don't know the impact this will have on society - we're all speculating. It's ridiculous to suggest that out of all the known-unknowns and unknown-unknowns, there will be no negative effects from gm.