I've used it, and had no problems at all. It's missing a few features before I can whole-heartedly recommended it over Opacity[1], which is what I use for the same purpose right now. Right now I'd need to make separate on/off state, for example, for each button. Opacity's factories & variables make that much easier.

That said, Opacity's development has slowed to a crawl. If the gentleperson(s) behind PaintCode keep it up, they will surely surpass it very soon.

[1]: http://likethought.com/opacity/