And this is not her fault, but picking her as VP runs the risk of being seen as a cynical ploy to appeasement Clinton supporters. Oy, I can already picture the hate dairies in my head. I don't agree with this: If she was a man I would want her/him to be on the ticket just as much, but it's something that needs to be taken into consideration.
With that said, she was seen as a potential running mate for Kerry in 2004 and was viewed as a potential Democratic contender in 2008, so clearly she's been seen as having presidential qualities for a while now.
I do see this point, and I've already seen that sentiment expressed by HRC supporters. My problem with that argument (and I know you're not arguing it, you're just stating it) is any woman that Obama picks is just being picked because she's a woman? For a campaign that's been crying sexism for a while, it's a bizarrely sexist argument itself. While clearly her gender fits into the picture, she's highly qualified and has been for a while as you pointed out.