I changed:
1) The database
2) The architecture
3) The adapter to my FUN third-party app
4) The framework
5) The model: lots of the core objects
6) The interface provider layer and flow
7) The state mechanism
8) The language :) yay Python!
The only thing I changed as little as possible was the interface itself. That's for the next point release ;)
And while I'm on topic, I got home at 5:45 :)