I personally think my last two reviews (that pony fanfic and my review of Eccleston's final story) went on for too long, so I'll spare you a plot synopsis.
When the Ninth Doctor regenerated, he was rather happy about it.
Contrast this to the Tenth Doctor, he was not happy about it at all.
When I originally saw The End of Time, when I thought about it afterward, this was what I did not like about the episode. I've since mellowed over this, though. What I also like is that Russell T Davies put the effort in to give the Tenth Doctor a 2-part adventure. But I'll get to the Eleventh Doctor's final story in due course...
Russell T Davies, for some reason, felt the need to incorporate some silly things in this final adventure, such as the Doctor locking the TARDIS like a car and the Cactus People (yes I know that's not their actual name), although I'll give credit they are plot relevant. Also, when the Master transforms everyone into himself (which is rather disturbing thought, everyone being made to look like John Simm), it's done with a silly effect of everyones' heads shaking rapidly back and forth with a knitting sound heard. Surely a face morphing effect like what happened in The Empty Child would have been less silly, albeit creepy.
I had trouble saying goodbye to David Tennant's Doctor, and for me, those feelings overshadowed my enjoyment of Matt Smith's first season. For some reason I got over Matt Smith's Doctor easier (it remains to be seen how quickly I get over Peter Capaldi's Doctor).
I don't know how, but David Tennant left an impression on the public and somehow became THE Doctor to our generation, similar to Tom Baker was THE Doctor to children (and adults) of a previous generation. What I don't understand is why he became everyones' favourite Doctor and not Christopher Eccleston, given the latter was the first Doctor of the revival. Probably because Tennant hung around for longer.