Besides the intrinsic win of the Doctor finally regenerating into a woman, I have some hope that the showrunner's regeneration will contribute to turn the series into one where the Doctor is the protagonist, not the protagonist and the MacGuffin and the Most Important Person Ever and ... and... As of late, too often Doctor Who has been about how the Doctor feels about the Doctor and that can be interesting in small doses, and turn into awfully boring as a narrative mode.
There's practically no limit to what sort of stories, scenarios, and characters can be found in any given Doctor Who episode (and, if nothing else, the visuals of modern Doctor Who have often succeeded in this regard); to say that it has recently failed to consistently exploit this freedom and over-indulged in the in-universe mythos of the Doctor as an engine of cosmic history isn't to spoil as much as to lodge a pointless complaint against self-satisfied powers-that-be.
It's my sincere hope that we might get a less narratively narcissistic Doctor in Thirteen; painfully enough, I hold this not entirely unlikely in part because it's difficult to imagine a contemporary show giving to a female character the sort of, well, entitled, angry authority the Doctor wielded at his worst moments. (The Doctor is so enmeshed with colonialist tropes that only the BBC could've come up with him. But I digress.)
Personally, I'm crossing my fingers for a Doctor for whom time travel is the premise, not the tool, dealing with problems with her wit, kindness, and knowledge, rather than overwhelming technology, a particularly blessed biology, and a reputation that spans galaxies and millennia. Problems that, ideally, she neither caused nor is the target of.
Doctor Who can tell those stories, and it never fully stopped. Just give me more of them, and a Doctor less worried about being the Doctor.