Enhanced Steam has over two million downloads and it turns out that having warning messages on the store page ends up being pretty effective even if it's in the hands of a small percentage of Steam's total user base. I've personally worked with a few developers who had questions about 3rd party DRM and how it interacts with Steam - several of which were convinced to remove their extra DRM because they didn't want the red banner on their store pages any more. I'd say that, overall, messages like that have been a success.
It's also the kind of thing that helps a program like Enhanced Steam reach more people. With the DRM example I see posts on Reddit/Twitter all the time like "Dude, I didn't know Black Flag on Steam required uPlay!" and a string of people telling them "Dude, you should have been using Enhanced Steam". In fact, that feature became so popular and such an issue that when Valve redesigned the store they included a section specifically for 3rd party DRM, although they sadly chose to make it yellow.
Anyway, it's something I'm working on and I'm also making it crowd-sourced so that there isn't just one person who says "Yes this game has a locked frame rate" that gets to be the authority (or police, as you will) on the matter. Hopefully it's another feature that proves popular enough that people take advantage of it, use it, and it eventually finds it's way into Steam proper.