I would agree it is two kind of seperate tales that feed into each other. The first half is a kind of Who
greatest hits but it's effective for the most part, like everyone else I know I hated the wikipedia style flashbacks, and yeah, Duncan makes a good foil for Tennant's Doctor. And yeah, the second half is where it gets really interesting. It displays exactly why these post-Time War time lords so badly need a companion and their humanity to keep The Doctor in check. Based on what we saw it looks as if the Doctor has regressed since the Christopher Eccleston days when Rose Tyler helped heal his wounds. All the losses and all the time travelling eternity has clearly caused a rift within him. "I am the master of time and it will obey me" sure sounds like the rantings of The Master, yes?
As for the specials...perhaps you are being too literal with the word. "Planet of the Dead" was entertaining & lighthearted while "The Next Doctor" was kind of somber and in some ways helped set the table for "Waters of Mars." Both "specials" could fit pretty well within any of Tennant's Doctor seasons but yeah, let's hope Davies goes for broke with the two-part finale.
Oh and how did you watch the thing? I thought you were the big one on patience and waiting.
And less a spoiler and more a really big tease from the RTD, Tennant & Gardner podcast for "Waters of Mars":Russell: ...because long ago the Ood said, "I think your song is sending soon,"
Russell: They knew, but how do they know? How can Ood be that psychic and that intelligent? How? What's happening? What's going on in the universe?
Julie: You big, big tease.
David: Time is running away with itself somehow.
Russell: You'd think something is bleeding, coming through from the other side. Very strange...
David: We'll have to come back and see what happens there...
"The most dementing of all modern sins: the inability to distinquish excellence from success."-David Hare