The reveal of the Final Five was what started to ruin it for me. The final five should have been entirely new characters, perhaps even the lords of Kobol. Essentially a third faction, apart from the humans and the Cylons, but connected to both. That was the first (and not the last) time when I realized the writers did not have it all mapped out beforehand and where just making shit up as they went along. I did like some of the other plot lines from season 4 such as the Cylon civil war, finding the dead Earth, Zarek and Gaeta's rebellion, and the final battle at the Cylon colony. Everything else to do with the Final Five, angel Starbuck, the significance of Hera, and finding 'our' Earth felt rushed and poorly explained. All the show's mysteries were explained away in the final hour with 'Oh, God did it!' which made everything from the previous seasons utterly meaningless. Identifying the final five with pre-existing characters meant creating extremely convoluted backstories to connect everyone together. And angel Starbuck came out of nowhere... But, overall, it was a good ride.
Aside from the God angle and a couple other things, it feels like BSG was what Voy was meant to be. Would watch again.
This is a no-brainer, but if you haven't seen Firefly or Dollhouse, I recommend that. I also want to reccomend a little known show that Fox also canceled called Liar Liar.