What changed since the last one? I can't see anything different?
Basically what I'm saying is that in its current form, almost no one will have a clue how to use it, regardless of how detailed any documentation is. From a user standpoint, having to do it in matrix form just doesn't make any sense.
So, what I'd suggest is changing it to something like one of these:
OK: A dialogue with 3 fields for rotation (in degrees) about the X, Y and Z axes. This would be ok for simple rotation tasks but tedious for anything more.
Best: In addition to the three-field numerical system, have a system where you select an axis you want to rotate it around (essentially radio buttons of X, Y, Z or user-defined vector) from the top menu, and then shift+click&drag lets you rotate the object around that axis in the 3d window. This system lets users very quickly define any rotation they want because of the real-time feedback, and lets them experiment a bit too.
(Oh and also, any operation needs to be undoable plz!