They literally listen to feedback and put smaller changes in patches, bigger in expansions. I put long list just from memory what positive changes SL made, especially in 9.0. Aaaand everyone ignored it and get back to bitching how Blizzard doesn't listen.
And only tiny fraction of feedback is useful. There are people that bitch about borrowed power and removing AP like system on same breath, there are people that complains about things that were fixed years ago (or fixed and reverted cause feedback turned out to be wrong), there is completely random noise that has nothing to do with reality (once I saw quit video where dude argued that... he HAS to farm Anima).