Ext 1 to 2 Migration Guide
Good lord -- what a mess. -_-'
I've got a LOT of code to change. However, just from looking over the ExtJS 2.0 examples, I have to admit that the new code is much easier to write. (Not that ExtJS was ever hard!).
The way that they consolidated many of the classes into larger ones is quite nice, and you can just tell from the examples that the new code is incredibly fast. Time to get to work.