I hate-watched this show.
From what I can tell, pretty much everyone I know in real life, the bloggers I follow, the forums I visit, EVERYONE hate-watches this show.
The characters are all horrible despicable people. They are not a normal representation of 20-somethings. I am a 20-something. Most of my friends live in Los Angeles, one of the most superficial and self-involved places on earth. And yet, I literally do not know any single person who is as wretched as Hannah on Girls.
You watch Girls in the same way people watch Jersey Shore. There is a huge element of schadenfreude here. The show is not that intelligent, it's really horribly acted, only occasionally funny. BUT, it is fascinating. You almost can't turn away.
I watched the whole series in a few days of marathoning and the whole time, I was thinking, "WHAT THE smurf. Seriously, WHAT THE smurf IS WRONG WITH YOU IDIOTIC PEOPLE?!" But it definitely hooks you in.
I wouldn't say it's enjoyable to watch. It doesn't make for a good time. But it's interesting and there's not much out there similar to it, aside from maybe Shameless.