I've never been really sure how I feel about Doctor and Rose together. Plot wise it doesn't make much sense, they are completely different species, and it's been pointed out previously to them multiple times how they couldn't ever grow old together. But Tennant and Piper have good chemistry, so I enjoy it for that.
The Cult of Skaro, in its prime, is one of those concepts that merits its own episode. War-gaming as the enemy as a way to find tactics to beat them. Alas, even now I'm getting flashbacks/flashforwards to the dodgy prosthetic makeup to come.