well i extracted lots of(~55) models from hl2 cs:s tf2 etc. using fbx import, due to lack of models that i use to test my scripts.

it never failed on uv mapping part, actually %95 of models imported completely(aminations,bones,uvs etc.) without errors. Sometimes(happened 1 times) vertices are not completely applied to bones, and sometimes it creates some extra polygons(happened 2 or 3 times) and mesh tester of MED finds them easily so its not a problem.

never happened to me but some people gets some arkward shapes instead of their mesh sometimes, but i think it has a workaround too.

edit: learning to unwrap models in max is easier than you think.