Hilary's actual performance in her job as SOS is irrelevant. If she chooses to run in seven years, or sooner if Obama becomes untenable to the the Dems (unlikely), then she will be carried to victory much the same way as Obama was last year. And, just like his inexperience wasn't a problem for the press, Hilary's poor performance experience won't be either.
If she has to run against Sarah Palin... she hopes to have stronger leadership and foreign policy credentials, so having anything less than success, weakens rather than helps. As Secretary of State, you either do a good job, or you fail. I am convinced that Hillary is the worst kind of political animal. Everything she does is a calculated move to advance herself, even at the expense of her party or her country.
When she was being vilified with negative stories about being marginalized and isolated by the Obama Administration, I think Dick Morris wrote an excellent article on that, for one, its interesting that within a week she suddenly 'had an accident'. If you notice, the weakened and marginalized Hillary before that accident, and then look at the empowered Hillary afterwards... I say the whole thing was cooked up as a dramatic event to result in a 'do-over'. I doubt she even scraped her elbow!