Just saw it on Saturday, I loved it. In fact, to me it served as a new ending for the series, even though its mostly set during Season 1 and 2 - its association with the two best seasons of nBSG (compared to the low point Season 3 and the sour taste left by the unjustifiable luddite fantasy of the finale and over-the-top angst that marred some if not most of Season 4) is probably the reason I liked it so much.
It was like a trip down memory lane, a year after the show ended (for me) and I really liked the ending and the look at how the Number 1s felt about everything. The two 1s floating through space whilst the monologue from season 4 played was just great.
Here is what I said in an email correspondence back when it came out. Spoiler
The film explores Cylon conflict. Not all of them are just about death and destruction. There are two Cavils: Fleet-Cavil, who wants to see the destruction of mankind, and Caprica-Cavil, who eventually changes and accepts that what they did was wrong. I hope you caught the parallel between the boy and Fleet-Cavil, where Cavil takes the fruit and kills the human-like part of him when murdering the boy, who is named John as well. This is perhaps cheesy, but I honestly like it.
There is a Simon on Caprica who wants to continue with the destruction and there is a Simon in the fleet who does not. The Simon in the fleet purposefully avoids Fleet-Cavil because he is not entirely committed to the Cylon cause. He eventually kills himself because of guilt and love for his wife.
There is a Six who is just as persistent as Fleet-Cavil in the destruction of the human race and another who is conflicted about framing Baltar. She ultimately decides to do it, though, but the conflict was there.
Then we have Boomer, goddamned fucking Boomer, who is perhaps the most tragic character in the series. She admits that she likes the Sleeper Agent life more than her natural Cylon life. She does not even kill the Old Man, and as the Chief said, she is a better shot. Boomer says that the only way she could go through with shooting the Admiral was to be like a Centurion, robot-like, emotionless. And similar to Cavil, she terminates the part of her that is human when she attempted to “kill” the Admiral. And as we know from the series, Boomer eventually begins to loathe the humans.
The above adds further character development. As Moore said when explaining the process of writing the series finale, the show is about the characters. That is what I like most about Battlestar Galactica. I really do not care about the space porn; I care about the characters and The Plan completely satisfied me in that department.
There is a bit too much archival footage, but like I said in my comment, I suspect that some of it was done for budgetary reasons. One can argue that maybe The Plan's writer ran out of creativity and decided to take the cheap route and include numerous scenes from the series. It is a valid argument to make and does have a lot of merit. Keeping that in mind, I still think it is pretty damned good.
