That certainly wasn't what I was expecting from all the talk of the prison from the comics. Did they jettison a lot of it, or is there a twist coming?
Basically this was pretty much straight out of the comics. A few details are different since the character load-out isn't quite the same. For one thing Andrea was never separated and arrived at the prison with everyone else--as did Dale, Patricia & Sofia. Michonne just showed up at the gates with her two "companions" and asked to be let in. Indeed from the previews it looks like if anything they're abbreviating Michonne's story.
As far as the prisoners go, no, nothing was really cut short as far as this episode's story goes. Unless you count that guy you just legged it. If memory serves you never saw him die, he just ran out the front gate and was never seen again. Oh and I think the alpha-male nut-job with the death wish was his "shower buddy", which makes his reaction a little bit more understandable.
There may or may not be something to do with them later on down the line that's been jettisoned as there's one prisoner in particular who wasn't present here but in the comics had something of a significant impact. I don't want to spoil anything, so I'll just say for those in the know that I'm referring to the one in jail for "tax evasion." Having said that, they could have shifted that plot to a different character.