^ Me too!
Actually, thinking about it more, the biggest appeal of a DW movie would be one that featured a past Doctor, probably Tennant or Smith. Think about it. We've guaranteed new, free episodes with the current Doctor, so no need for a film there.
But, what about a story centered on a past Doctor? An episode won't be centered around a past Doctor. So, if the only way to see say a new Tennant story is at the theater, that's quite a draw.
Of course, that may depend too heavily on the TV fanbase to be profitable. I'm not sure about that angle. But, as a fan, that scenario would probably be the most exciting. A new Tennant or Smith story.
Although, I'm sure I'd see it regardless!
Mr Awe
Much as I love Smith and Tennant's Doctors, I still don't think that their presence in a movie will prove a big box office draw for DW fans.
When Star Trek TNG was on the air, the two Star Trek movies released during its run (TFF and TUC) didn't do particularly well at the box office. TFF's flaws are well known but TUC is one of the best in the original series of movies and was not only a chance to see the original crew on the big screen but the final chance to see them all together.
Similarly, GEN, FC, INS and NEM were released when one could see the DS9, Voyager or (Archer's) Enterprise crews on tv but had to go to the cinema to see Picard's TNG crew. And despite the popularity of Picard and Co, those movies didn't do especially well either. NEM in particular bombed, again, despite being the final outing for one of Trek's beloved crews.
Personally I blow hot and cold on a DW movie. As Starkers said, I don't know what it will add to the tv show, other than a bigger budget and better SFX.
I'm inclined to think that a standalone movie, effectively borrowing the concept from the tv show, but not set in its continuity or bound by its history, is the way to go; cast a well-known British actor as a sort of alternative First Doctor in an origin story. But equally, I'd happily argue the or concede the points one could make against such an outing. My overall instinct is that DW belongs on tv and long may it continue to air there.