I've finally seen the first episode and I loved it.
As a big fan of the comics I was afraid the TV show would ruin it but my biggest concerns (bad acting and shortcuts) disappeared quickly while watching it. I like the format, long episodes (more than an hour) allow to develop the stories and take time to make it evolve. The actors are pretty good too.
The atmosphere is really well retranscripted, it's funny how the show is both extremely resemblant to the comics and yet different with additional scenes or modified storylines. I thought all the modifications were good since they were more suited for TV or simply more coherent in terms of the story development.
For example, the tank scene is not in the comics but it's just great, you can feel all the tension and horror surrounding Rick and how he barely saves his life.
It's also great to see that they have not turned it into a "basic" zombie show, like a zombie appears on screen suddenly and you're scared ; no, they've stayed true to the spirit of the series, which is not to scare but to make us think about the characters and their evolution in this crazy, dead world.
Plus the zombies are very well done, it's amazing it looks like a movie more than a TV show!
Finally, the music was discreet in this episode but I liked what I heard, sounds like the great Bear Mccreary (Battlestar Galactica) is back to work!
Can't wait to see the next episode although I know what will happen!