I know she's not as conservative as some may like but who else can beat Hillary in '08. If Jeb gets the nomination, the media will have a field day "It's time for a woman POTUS" "world's smartest woman" and "Bush Dynasty". Unfortunately, Cheney is too ill and Rummy is too old. Guiliani is too liberal and there's not a popular big state Governer to be found (Taft and Pataki are tacking hard to the left and will be lucky to be re-elected.)
The only thing that matters is keeping Hillary out. IMHO, Condi is the only one who can do that.
Besides, she is damn impressive and deserves it.