I have a book through Apress as well. Among other things, their contract was pretty generous about my repurposing small chunks of book material for other purposes--which I've taken full advantage of. They also offered some sort of discount so that an organization could have me do a book signing though I don't know the financial details. (And said organization might have done this if it weren't through a known publisher.)

On the other hand, the price is set quite a bit higher than I would have set it personally for maximum exposure. And I don't have the right to broadly distribute free electronic copies to just anyone I want.