I have moved from tipfy to webapp2 for appengine projects. Both of these frameworks are created/maintained by Rodrigo Moraes, who in my mind appears to be a super hero, in churning out a couple of very decent frameworks. I ended up with webapp2 and that is what is recommended. tipfy just went through a large update and a lot of things changed.

webapp2 is super easy to setup, it is a single file and pretty much extends webapp. Include the extras, through in a couple of libs (eg Jinja2) and you are good to go. All the functionality you need to get going developing a half decent web application on app engine.