I have to admit that I was a huge crammer, and it did help a lot...
On my first practice test I scored in the 450 range on verbal, so I panicked and systematically went through the entire Barrons word list and made a ridiculous number of flashcards (I don't even know how many...1000? 2000?). I made the flashcards a few months in advance, but didn't really study them in earnest until the last 2 weeks leading up to the test (I probably "learned" about 500 words in the last 5 days). I ended up getting 710 on the actual thing, which was a HUGE improvement.
Although I can't really recommend the cramming from a health perspective - that much stress can't be good for anyone! - it really did work, and a lot of the words I studied ended up on the test. I would especially recommend studying the past tests, because a surprising number of words I got wrong on the practice tests showed up on the actual one.
On the other hand, I can totally see where the haters are coming from...if I had a naturally great vocabulary I'd be annoyed too if someone who crammed for 2 weeks got a similar verbal score. But I also don't think that those who have not been exposed to obscure words, for whatever reason, should have to resign themselves to having a low GRE verbal score on their grad school application. The GRE is a silly and somewhat arbitrary test that may or may not be a predictor of grad school success, and I think students are justified in using any study method that will work for them.