Missing documentation of a backwards incompatible change from 2.x
The removal of old SelectModel.annotate() method is not listed under the list of backwards incompatible changes. I had to actually dig through the old 2.x documentation to figure out what that method used to do. Perhaps the current documentation could at least link to 2.x documentation on the 3.0 changes page in regards to this method (when noting it has been removed).

Edit: Same is true for "upsert()" on insert by the looks of it (sans the fact that there are obvious alternatives in existence).