Sometimes poor and outstanding service is not even "crew" by crew, but by individual flight attendant.
There are times that I provide excellent service, but my coworkers on that particular trip are absolutely lousy. And sometimes I have bad days too. Stews such as myself understand the flyertalker perspective while flying, while many have no clue whatsoever. As an individual FA, I can only do so much.
So, when filling out your comment cards, before crucifying an entire crew, please be absolutely sure that it is the entire crew and/or specific FAs. Even the "lead" FA is not a supervisor and in regards to the crew is just there to coordinate and be a go to person.