Finally figured out what bothered me (SPOILERS)...
So, I watched the whole season and something was annoying me the entire time, but I couldn't figure it out. It really bothered me that Mickey and Gus got together - or more so that Mickey picked Gus (although, she is a flailing addict and he's a pretty convincing fake nice guy). I knew it wasn't because he was so awkward that I was second-hand embarrassed (which he was and I was) or because she's "out of his league" or whatever like some reviews have said. Finally, in the last episode I figured it out. They wrote Gus like one of those *horrible* nice guys (about 5% of nice guys are horrible, *beep* nice guys). Like the kind of guy who seems really nice and goes out of his way for people in his life, but it's pretty self-serving so he can get what he wants from them. Not all of the time, but at least 50% of the time his character seemed that way to me. He seems to me like the kind of guy who would latch on to a girl like Mickey and help her move and find her cat and try to save her and then get pissed when she went on a date with someone else even though they've always been *just* friends and he's never pursued anything beyond friendship. The kind of dude who would eventually imply something like, "I'm so *beep* nice. I'm the nicest guy ever, you stupid bitch. Why won't you *beep* *beep* me?!".
I realized that this is the vibe I got from his character sometimes when Mickey was in tears telling him about the plethora of issues she was dealing with and saying, "I need to be by myself for a year to work on my issues and figure myself out" and rather than hearing her valid concerns and recognizing copious cries for help on her part, he grabbed her and made out with her. She just told him what she needed, but he did what he wanted instead of listening to her. It, for me, was very true to how he had treated her for the entire show. He met her, fixated on her, and then got mad at her for not being exactly who he wanted her to be. You wanted to date a human person, but expected her to not have flaws and love magic just because you took her to the show? I mean, Mickey is wildly flawed, but at least we see her at the crux of her addiction. Gus should be functional, but is this crazy dichotomous mix of narcissism and incurable self-doubt. He even yelled at a *beep* 12 year old who told him multiple times that he was her best friend. Mickey definitely hurts a lot of people in her life, too, but they could not make her enough of a "villain" (as hard as they tried toward the second half of the season) to make her more selfish or annoying than Gus.