I know pretty much everyone on the (now 70+ person!) dev team reads this subreddit pretty frequently. Personally I check it several times a day.
I love it. I love reading stories about people having fun with Hearthstone or exploring new decks. I also love finding opportunities to make the game better. I send every bug report and suggestion to the different teams responsible to make sure we are tracking them. They assure me it's redundant because they are also reading Reddit daily (and most reported bugs have already been caught by QA) but I don't want to miss anything.
Sometimes we disagree with a particular post, and one of the biggest pitfalls is believing that one person's perspective (or even a couple thousand people, in the case of a highly upvoted thread) is representative of everyone. I think it sometimes inspires fervor when people believe that everyone thinks the same thing, so how can we be deciding something different? Reddit is especially powerful at drowning out dissenters through up and down votes. And certain categories of player are just not represented here at all. That's usually irrelevant, because the feedback is helpful either way, but it can amplify a feeling of "community vs developers" which has always felt strange to me. When we go home, we play Hearthstone. We're part of the community, too. I like to feel like we're working together to make the game more awesome.
I also notice that sometimes when people don't have access to the whole picture, it can inspire an angry position. It doesn't always happen, but it comes out as: "I can't imagine any reason for you to do this. The only possible reason I can come up with is that you are bad developers, therefor that must be what is true." This is the hardest feedback for me personally to read. I'm lucky to be able to see the whole picture, so I can see the reasons behind these decisions. This phenomenon is the biggest reason I love interacting with players. I think just hearing the other side of things can take it out of that zone of "you must be idiots" to "oh they actually had reasons for this". Important to note that people often still disagree with those reasons, but it becomes an informed conversation at that point, which is awesome.
Arena Balance is one thing that has received a lot of attention recently, and has spawned a lot of discussion internally. We had plans for tools that would let us make changes in the medium-long term, but the online discussion has made us stop and rethink our timelines and options. That's honestly great. Hoping to have something to share on this in a couple weeks.
Yeah, sometimes there is negativity. But there is always something for us to learn in that, and so we come back every day, hopefully with a curious mind, hoping to find ideas that we can take back to keep making Hearthstone better.
Also who doesn't love Day9 highlights.