Gimp of 01:

Yes, we usually wear sandals, crocs, Keens, etc. in the canoe but don't trust them for stability on the portage (unless it's really short and easy). So the change into hiking/portaging boots makes us feel more secure (it might also provide a little protection against poison ivy, who knows?).

It definitely adds time at each end of the portage to do the change, but we feel it's time well invested.