Yes, the characters are not always likeable. Marnie is in my opinion the least likable. She was positively gleeful once she realised she was putting a wedge between Desi and his girlfriend. The look of delight on her face at the end of season three when she saw them fighting. It was a little disturbing like she was feeding off the drama like the witches feed off souls like in Hocus Pocus.
Hannah is annoying, selfish, mentally ill, and sometimes baffling but she's not the worst person to ever walk the face of the Earth but the way some people whinge online you would think she was the most terrible human being ever. I find it weird that people watch shows like Breaking Bad and cheer on Walt as kills people and then melts their bodies but when Hannah does something flaky the pitchforks come out?
The hatred for the characters on Girls is a lot like the hatred that was directed toward Skylar White back when Breaking Bad was on. People had an irrational hatred of her as well and it made no sense. She finds out her husband is a drug lord, a criminal, a meth cook and a killer and she does not react well and she's a bitch because of that? I found it fascinating that so many people thought she was the more shittier human being for having an affair and not "supporting" him compared to him being the Darth Vader of the Meth world.
Why do so many people cheer on characters like Walter White but mock and complain about characters like Hannah from Girls goes nude or ditches her friends to go and do something selfish? How is Hannah the more terrible human being? Hannah is a typical, self-centered, slightly spoiled young girl who is used to a certain level of entitlement. She is raw and real. And that is what makes her such a well written character. I don't hate her for her flaws. I find her flaws fascinating. I went and saw Fifty Shades of Grey yesterday at the cinema and I was talking to my husband about it afterwards and how I felt that Ana was a bit of a blank slate. Anyone could be Ana. "Oh I study English Lit and work in a hardware store" it's like the author spent five minutes fleshing out her character. Now Hannah, on the other hand, is so detailed, so fleshed out, I could talk about her for days. Love her or hate her but you have got to admit she gets people talking and that is the sign of a good writer.