Season 4 was just crap.
Season 1 was amazing - I know some hate season 2 but I enjoyed it because it showed that escape is just the beginning and how much Michael had actually planned in advance and so it worked.
The problem was where to go from there, he'd escaped prison and the show was called prison break, so erm yeah lets just throw him back in another prison. Season 3 just felt like they where trying to make something like season 1 again but it didn't work.
Season 4 was the worst though it seemed like all of a sudden prison break had become a Mission Impossible/Oceans Eleven type series and it was just too different. It got cancelled to and basically had to try and finish it all.
To me it went downhill after the second series - it seemed that they hadn't planned that far ahead. The worst part for me was when Michael worked out what Scylla was in a dream. It just seemed everyone had lost the plot. But they finished it all up and tied a few loose ends apparently in the special they did (still not seen). There is no where for the story to go now and I feel brining it back would further more ruin what started off as great.