The Walking Dead did begin as a comic book, and the pilot is certainly filled with lots of gore, but otherwise it fits right in at AMC for one clear reason: like the titular zombies, it moves very slooooow. At an hour and a half, the pilot has far more long silences than dialogue or action, setting the mood beautifully but not doing a ton for the plot. Most of the major characters beyond the protagonist are limited to a single scene, and the protagonist's lengthy walks around his ghost town might as well be happening in real time.
That said, it's not necessarily a bad thing just yet. This isn't a Rubicon case where we spend a half hour staring at a parked car and aren't entirely sure why. The silences do very much put us in the world of Rick Grimes, a sheriff's deputy who wakes up in the hospital after recovering from a gunshot wound to discover the world around him has greatly changed. There's a whole lot of emptiness, but the only signs of life come from those very much no longer alive. It may be pretty similar to the opening of 28 Days Later, but it's still effective.
Once he finds other survivors things pick up considerably. On a quest to find his wife and son, Grimes runs into a father and son getting by after their wife/mother joined the ranks of the dead. And we soon find out many of the people from Grimes' previous life are out there in a survivors' camp after all. Personally, I'd rather see what happens once Grimes meets up with them, but I get a sense that's how this 6 episode run will end.
If 6 episodes seems short for a first season, here's why it makes sense: this feels way more like a miniseries than a full series. That doesn't mean there's not more life in the show. It could turn out like the miniseries that initially launched Battlestar Galactica which, by the way, I didn't like nearly as much as the series that followed.
Ultimately, Walking Dead's pilot was strong enough to keep me going, but I'm not yet entirely sold. If the moodiness and slow pace of the pilot were intended to make an impression and help this stand out from other zombie things we've already seen (and there's not much else in the plot so far that does), then I'm cool with that. But if they really expect us to accept Rubicon-style pacing in a show about zombies (and zombies that are more sad than scary, for that matter), then I'm not so sure I'll be in for the long haul. Let's see how episode 2 goes.