I'm okay with the choice for Tennant, even though I just watched the two-parter not long ago. Definitely my favorite story of all the nuWho stuff. A terrific outing that's full of fan-wank.
To be honest, I really don't care what they show for Smith, as I've just never really gotten into his performance.
I've really come to enjoy these specials and it's a shame they won't continue next year. I'd love for them to do Classic Who eps, one Doc per month, on a regular basis.