"Guts" was a damn good episode, definitely maintaining the pace from "Days Gone Bye." I'm very glad the tv show kept in Rick's idea from the comics of trying to "blend" with the walkers by smearing entrails and blood all over themselves. Glenn in the show so far seems to be just as brave as the comics version too. Merle Dixon was an interesting addition to the tv show, for already presenting the idea that sometimes a person may have to be left behind to save the group. I didn't see the preview for the next episode and I've attempted to avoid reading too much about the series (I've read through issue 54 of the comics, so I don't want to accidentally surprise myself on anything created for the tv show), so I'll be curious to see if he manages to return to the camp.
They'll have to develop new nemesis and story-lines fairly quickly as the walking dead themselves don't present viable or even interesting long term antagonists, but they'll suffice for the first half of this season.
The comics have had plenty of outsiders for Rick's group to contend with, so the show has many possible nemeses to adapt in future seasons.
Edited to add:
Here are some interviews some people might find interesting:
Producer Gale Anne Hurd
Sarah Wayne Callies