I enjoyed the premier. Both stories were good. Personally, I hope they don't wipe out everyone but the main characters and the leave the prison, I like the idea of them having their own little community there.
The stuff with the crazy lady in the woods gave us a good look at what Rick has become. The rain of zombies in the store was a pretty cool sequence. I like that they are trying to come up with more interesting zombie run ins than just a herd coming up on them while they're in the middle of doing something else.
I'm thinking that the virus or whatever killed the kid is the new threat they've been talking about in all of the promo interviews. I didn't even think about it being The Governor attempting to sabotage them, but that would make sense.