In a word, amazing. I can't even begin to say how happy I was with this first episode. They stayed close to the source material to start, but added some very real pathos at points that I felt weren't quite there in the comic. The actor who played Rick Grimes nailed it in my opinion.
My concern, however, is with Rick's wife Lori and Rick's partner Shane. Their presence in the first episode felt forced and I was less pleased with their portrayal's. The guy they picked to play Shane just does not work at all so far, and I worry that the love triangle there might last longer than I care to give a shit about it. They say the show goes in some pretty different directions than the comic, and the most likely changes will probably be in regard to which characters get killed off, because TV audiences (and Blogust) grow too attached to characters and storylines.
Still, so far so good.