Surgery - almost zero help from Uworld; need medicine
Psych - ??? I take this Friday, but I've heard not helpful
Medicine - good, but I'd supplement with MKSAP too
Peds - good enough
Neurology - good enough
OB/GYN - haven't done yet
Like someone else mentioned, everything else besides medicine (and maybe peds) doesn't have enough questions so you need to supplement. I don't think I knew anybody that only used UWorld for studying for shelf exams.