Watched this over the past couple of weeks, it's sort of brain-dead entertainment with huge numbers of plot holes. Lets' be honest here the only reason I watched it all is because of nostalgia for the earlier seasons and I could kind of just kick back without thinking too much. Some of it is so preposterous but it gets away with it because it just ploughs straight on, if you stop and think about how stupid bits of the plot are you've missed the next pivot.
Having binged Breaking Bad and BCS over the the past year the pacing is completely different, basically everything changes over the course of an episode. And I'm fine with that in general, I liked Strikeback for the rollercoaster action etc.
It's definitely run its course though, one of the challenges with this show is the need to shoehorn a prison in somewhere because of the name, and the fact that they can only bring back characters so many times from incarceration / death etc. Like T-bag is a great character, but how many excuses can keep being made for him being around?
I can remember hardly any of what happened in PB seasons 3 and 4, and I suspect S5 will go the same way.