Vocabulary review--are flash cards (or SuperMemo) helpful?

The antimoon guys are very high on using SuperMemo to review vocabulary. Other people use similar software. Many use flashcards, or even vocabulary lists.

My question: Is vocabulary review really helpful? Or are you better off spending the time doing more reading or listening, even if you have to look up words again? (And/or figure out words in context from repeated exposure in context.)

I used to be obsessed with word learning - and I didn't do it badly either - but it just doesn't work as well as exposure, as long as the exposure is of the useful kind.