I briefly went on /r/serialpodcast and they were all up in arms about the "Rumors" episode too. I don't get the hate for it honestly. So far, Koenig has pretty well laid out how conflicting all the available evidence and testimony is and has essentially said all along that she cannot come to a final conclusion on the matter because of it. "Rumors" was her looking at the character of Adnan and also searching for any scrap of history that would jive with him being a stone-cold killer. Seems like she pretty easily wrote off the rumors as either baseless or inconsequential. Also, like Johnny said, ruling out the possibility that Adnan is a psychopath is equally important for the listener's perception of him. Lastly, reading from the letter Adnan wrote her directly combated a lot of accusations about how he has behaved in the interviews in past episodes (i.e. "Why isn't he frothing at the mouth at every turn about being wronged?!").
No, it was not an episode with all sorts of juicy new facts and evidence, but it was extremely useful in taking a look at who Adnan was and is. Since we are extremely unlikely to get a smoking gun, or rock-solid alibi next episode, and given the murky nature of what we do have it seems obvious to me that most people's opinions are going to rest largely on their perceptions of Adnan.
For my personal take, as I've not weighed in yet, at the very least I think he should not have been convicted based on the evidence and testimony provided. There was an inordinate amount of reasonable doubt that should have gotten in the way of that. That being said, he wasn't found not guilty and as I understand it, there is a higher bar to get the sentence overturned and I'm not sure he's able to meet that bar. My sense is that Jay is clearly more culpable than he says and that Adnan is probably innocent, but there has to be some substantial piece of information that is being hidden to explain it; the case as we know it doesn't seem to provide a motive for anyone else to want to kill her. Being that it's 15 years after when this information should have been sought out though, I think it's highly unlikely that it will reveal itself unfortunately. For all we know, Hae's last boyfriend could have been the jealous type and was good friends with Jay so they set out to kill Hae and frame Adnan. Fat chance of that ever coming out if it's the case though.
All-in-all, I'm under no illusions that this story is going to wrap up neatly with a bow. I fully expect the last episode to be largely about how it's impossible to come to a firm conclusion with the available facts and what that means legally. Koenig will probably address the unavoidable criticism that her first season didn't solve the mystery it set out to as well. I suspect it will end with an aside on the innocence project people's efforts on Adnan's behalf. It's possible Koenig's withholding some key piece for the last episode, but I doubt it. I can't say I have a single complaint about this show though. It's been fascinating from day one and I've loved every moment of it.