The docs space is equally dizzying: there are classy looking products that only solve a narrow slice of the problem. e.g. Readme.com is slick, but to use their analytics you have to send them data. They don’t solve for API key management or other gateway pieces at all.
Open source solutions like API Umbrella can solve the whole thing, but with less polish, no SLAs, and taking on responsibility for someone else’s esoteric stack choices. I have enough trouble with *my* esoteric stack choices :)