Certainly this can help you in the AWA section; the sophistication of your writing can certainly impact your score.
Having a good vocabulary in general helps on almost every section. I remember a Sentence Correction question that had the word "synaesthesia" as the subject of the sentence, and the students who did not know the meaning of that word were unsure whether to use a singular or a plural verb.
Additionally, with the time crunch of the GMAT, getting slowed down by alien-looking words on Reading Comprehension can lead to trouble.
Ultimately, though, at some point, your vocab is what it is. This is not the SAT, which pounds with you vocab words that are just over your head in sentence correction format (or analogy format for those who were in high school back when).
If you're just brushing up because you feel confident with other portions of the test, I won't tell you not to, but I think there are many ways your time could be spent more efficiently besides studying vocabulary words.
