I was disappointed by season four. There was certainly some good stuff - I enjoyed Home, the Vulcan arc, the Babel One/United arc, Observer Effect, In a Mirror Darkly, and the Demons/Terra Prime arc.
A lot of story momentum was ruined by crappy concluding episodes. It happened with the Augment arc, though to fair I never felt particularly invested in that one. The worst one, I thought, was The Aenar. All of the interesting storylines ended in United, yet they carry on looking for this albino Andorian?
Affliction had a boring conclusion (don't even mention Klingon wrinkles), and IaMD went on an episode too long (even if it was to help he budget).
Storm Front was dull, as was Daedalus. Bound was terrible, and TATV always has its own thread for the amount of problems it as.
The episodes that are left that I like, are all basically fanwank. I think it comes across as this because it all came a bit too late, and also because they did too much of it. Ideally, these kinds of episodes should have been dribbled throughout the show's run, in order to continually build towards something.
It was better than seasons one and two put together though.