@Rob: could you see if 'simplify' can be included into your pretty undo functionality?

[katjaq]

it might be great to have an undo-possibility for simplifying the region path ((for the moment, you can simplify the path; but if you are unhappy with the result (maybe too imprecise now), there is no way of going back ((you could just manually add points to the existing current unhappy path and then go by hand to move the points to outline your region more precisely again...))
I could hack a one-step-back thingy into simplify, but it would be most awesome if you found a way to include simplify into your pretty undo :)