I just saw Water of Mars for the first time (the supposedly complete torrent I downloaded before didn't have the specials except for the End of time), and holy shit, the ending was awesome.

They've made it a point to show Tenth's dark side from time to time, but all of the other times were just glimpses and they're usually against the villains, so it kinda makes you still root for him, but the "timelord victorious" scene was plain scary.

The doctor at that point has his feet in villain territory, but unlike the usual crop of bad guys, his motivation is not a lust for power. He was just tired of losing his loved ones and being powerless against change. He's very lonely, frustrated, and scared. Tenth became very human towards the end of his life.