She certainly had a lot of exposure to international affairs and international diplomatic outreaches during her 8 years as first lady. During her 8 years in the senate she has served on the Armed Services Committee and she served as commissioner of the Helsinki Commission (US Commission for Security and Cooperation in Europe).
She's also known worldwide, and she's as tough as they come. So I think she'd be an exceptional person for the job, especially if it comes down to sitting down with diplomats from hostile countries.
Her passion may be health care reform, but honestly very little is going to happen with that as long as the economy is disastrous. And with people around like Howard Dean, Ted Kennedy, and Tom Daschle, she's not the only person with towering credentials in that field.