This episode sets up a lot of dominoes, poses a lot of interesting questions -- too many, in the end, to answer in one episode, but several which are very good.
A welcome change from episodes where the questions are practical -- how do we get more fuel? how do we escape the Cylons? -- to an episode where a more philosophical question arises: if a mysterious stranger offers you the chance to end the war, to escape from the Cylons, to find Earth, only at the cost of giving up control, should you do it? At what price does salvation come too high? What profiteth a man if he gain the Earth and lose his soul?
This episode does a great job at building and sustaining suspense -- fuzzy med scanners and mind-reading and telekinesis. But the ending -- Gaius Baltar's dramatic return -- perhaps lacks a little motivation. Sheba's immediate submission to Count Iblis also seems a touch contrived (and hardly a good vote for the character of a female pilot only recently added to the cast line).
But all in all, the episode asks some questions often overlooked during more straight-forward survival missions. This reflection deepens the characters, and raises the stakes of the plot.