When my girlfriend told me she was going to start watching this show, I figured it would give me 60 minutes a week to myself. But when I actually watched part of the first or second episode, I was surprised to find myself starting to get drawn in.
Here's what I like about this show: First, the kids talk like kids (even if some of them look like adults!). I don't know about anyone else, but after Dawson's Creek and The Gilmore Girls, I find it refreshing to see a show about teenagers who have trouble expressing themselves instead of speaking in pithy, self-aware sound bites.
Second, this show does a believeable job of presenting the class issues involved in having a "poor kid" move in with a "rich family". Others have pointed out that it avoided the initial cliche by having the two teenage boys become friends, but later episodes have shown that in spite of their friendship and common interests (e.g. comic books), there are still deeper issues of class and sexuality that show how different their "worlds" really are.
And finally, I was surprised to see that the writers were actually able to make me care about the problems of the rich characters! (The adults, anyway). For too many nighttime soap operas, portraying the "problems of the rich" are just a way to get us "unwashed" types to sneer at the "problems" that money brings ("I wish I had those problems!"). In "The O.C.", the writers actually explore questions of money, class (again) and love in the various adult couples in a way that brings Jane Austen to mind; we can relate to the struggles the characters are going through even if their day-to-day lives are completely foreign from our own.
All in all, a surprisingly enjoyable TV soap opera that doesn't require you to check your entire brain at the door.