I love PausenClown.
Its small, its fast, its light weight, its simple, has a cool look, everything you would expect from a mac software.
It is very good to make small notes. I use it to save some info that I dont know where to save, like things I want to buy, to do, to search on the web, ideias, funny things, etc.
I miss a [command + ,] preferences, maybe a opacity control (although I like the default very much). But again, I love its simplicity too.
For the developer, a few problems to check. Instability. It crashed a couple of times, specially when openinng it. The search (why not [command F]?) cant find properly and leaves the page blank unless you click on the x inside the search box. Save, or auto-save, only works if you move along the left items bar. I mean, if you create a group called songs, inside it you put "song a" and quit the program, it wont save the text "song a". Maybe a [do you want to save] box before quiting would solve the problem.
Hope I could help :D