I'm another one of those who refuse to believe that Jack becomes the Face of Boe, but I love this story anyway. Jack here is very believable as someone inconceivably ancient and changed by the years yet still with the same core personality. I appreciate the fact that he WAS joking about being the Face of Boe in LotTL, but was unexpectedly proved right later. I'm amused at how unexpectedly surviving a near-regeneration situation has put the Doctor's mind thoroughly in the gutter in addition to the physical reaction. This is a lovely mix of humor and genuine emotion.