Like I said, it’s a kind of experiment right now. The projects I’m using it in aren’t completely public, they’re for our client base, and I’m not terribly worried about user stylesheet issues.
The biggest downside is obviously the number of classes attached to an element. But I find it much more maintainable than any alternatives I’ve tried.
The main thing I’ll say is this; it works best when you can start off a project with very complete initial designs. We happen to have a very good designer in our company who creates wonderfully consistent designs. It was off the back of them that I decided that I could create a library of helper classes which would allow the creation of new features in a very short time. And it has worked well so far.
I’m working on a configurable library to allow others to try out my specific idea (which I wouldn’t say is exactly Atomic CSS). So it’s yet to be seen if other people find the value in it that I do.