Good episode -- I think it is good that they had Herschel wake up. I had a fear that they were going to go 5-6 episodes with him out of commission, with tons of scenes/time of folks sitting bedside with him and the continual possibility that he would wake up and turn.
I like what they did with the prisoners. This shouldn't be much of a spoiler for the folks who haven't read the GNs, but having the character "Tomas" was a nice mindfuck for those who have.
I'm actually not looking forward to next week's Andrea/Michonne-centered episode. I wish they'd spend a lot more time at the prison, as there was a lot of good stuff that can happen there and I'd rather see them kill some time there (building up a sense of community and security/stability).