I've been reading the comic for almost three years now. I've tried to get into other comics that Jeph suggests, and I do read
http://www.agirlandherfed.com/ regularly, but no comic has had quite the same appeal for me that QC has.
It's not the indie rock thing, because I'm an opera singer and rarely listen to anything but classical music. Some of the time, I have no idea what the joke is about, but I enjoy the comic anyway. Although there is more elegant art out there, I like the clean simplicity of Jeph's art. It's always clear who's talking and what they're doing and I always know who a character is, even if they're wearing a different outfit or they changed their hairstyle, and that's more important to me than pretty pictures. I've also enjoyed watching the art evolve over the years. Mostly, I like the characters because they're so real. I feel like these are people who could conceivably exist in real life, though I wish I could afford such an awesome apartment as Marten and Faye have, especially given that they probably make minimum wage. There's just enough suspension of disbelief (AnthroPC's, Vespavenger, etc.) to make it an interesting world, but the people in the comic are real people with real problems and believable personalities. They're my age, struggling to figure out who they are and what they want, just like me and everyone else I know.
From the comic, newsposts, and my recent exploration of the forum, I get the impression that Jeph is a down-to-earth guy who isn't trying to be something he's not, and he writes his characters the same way. I appreciate the honesty of that.
This went on longer than I had planned...I hope I got my ideas across to anyone who happens to read my post!