I was putting EMT in a Bell box the other day and I tried one of those offset connectors. I got lucky that in one end it lined up right with it wrench tight but if I had needed one on the other end I would have been in trouble. Made up tight without a lock nut it was about 90 degrees from laying against the wall and with a lock nut there weren't enough threads engaged to actually tighten it up.
Usually I just bend an offset but I was trying something new.
