I’ve been using and contributing to kivy for some time, and using it for a big application intended for market. Although still not as complete as native developpment (not sure if using the map Android API is possible at all, but there are alternatives), it works very well, with good performance. The kv language for rapid prototyping is really cool.
And as bonus points, your apps work on windows/linux/mac/ios too… (we still have to try getting on apple store, but technically it works). edit: to this day at least one kivy app has been accepted on apple market, look for “deflectouch” if you are interrested.
As opposed to SL4A, you get a real apk to distribute, with kivy as well as a very nice and slick GUI api, fitted for multitouch apps.