Yeah, I really enjoyed Tennant's heartfelt moment. It was magical
A lovely little episode and makes me all nostalgic for the older episodes of Doctor Who. As I'm quite young, I can't remember distinctly the few old epsiodes that I watched as a child (I just have a mild memory of lots of dashing around and some wild, silvery sets...and Davros. I definitely remember Davros!) Methinks I'll have one day watch it from the very beginning. (I also liked Tennant's comment -- "back when I was trying to be grumpy and old and important, like you do when you're young!")
And yes, I think, after the success of this small snippet, a longer episode with two or more Doctors would be very interesting.