It's so stupid and such a letdown after 6 good-to-great (yes, I think "42" is good and will defend it in long-form some other day) episodes in a row that it ends with... that.
I had hoped that, given time, I'd be able to see the episode for more. That maybe it was just my dislike of episodes where the Doctor is not the star? Where the Doctor is not his usual energetic self?
Nope, it's more that it's just ridiculous and creepy and can't balance out to good versions of ridiculous and creepy at that.
The weird The-Doctor-Now-Lives-In-A-Tent-And-Responds-To-A-Bell situation turns into the bizarre Dobby-esque Doctor that's only followed by the even worse Tinkerbell-esque Doctor that has extra super-powers on top of regaining his youthful appearance? Usually, Russell T. Davies is very good at putting emotional meaning behind his plot holes to a point where you don't care so much about the hole. But it's just not there in this episode that bounced painfully from dark and disturbing to saccharine and just... stupid.
Not to mention just a complete letdown for finally having the Master in it. I don't think RTD could ever quite find a way to balance the Master's insanity with actual plot. The End of Time didn't do much better- a little bit better, but not by much. And a lot of that comes down to having more emotional impact via Wilf, Donna, and knowing that Tennant's era was ending.
The only saving grace is Martha getting appreciated. Re-watching Martha's run really makes you feel terrible for the girl, as the Doctor treats her terribly and a lot of shitty things happen to her (and even more happened to her on Torchwood and in later episodes). And, yes, she is fully responsible for Professor Yana opening his pocket watch and I don't understand why she didn't just grab the damn thing from him the moment she recognized it and she she'd take it to the Doctor to be checked out). But at least, in the end, she gets to be bad-ass and break free of her one-sided terrible relationship with the Doctor.
But that's not really a great note to end a series on, is it? Or a great continuing theme.
I do, however, now feel less hatred towards Jack being the Face of Boe. So, there is that. Yay?