Tipfy is nice, but its documentation is horribly out-of-date. The last time I tried using it, I had to dive into the source code several times to figure out what was going on. Eventually I ended up moving off of app engine. (I considered contributing to the docs, but I would have had to spend a lot of time learning the codebase as parts of it had been heavily restructured since the docs were last updated.)

Agreed. Tipy is awesome! http://www.tipfy.org/

Yes, but the documentation is a little out of date as the current version has changed significantly. Basically, don't go by anything you find on the web, make sure you use the docs/examples in the mercurial tree