What is Tim Geithner like?

As you've probably heard, Tim Geithner has been nominated to be the next Treasury Secretary. As he was my boss for several years and I had the opportunity to brief him on a couple of occasions, here are my five cents.
The first impression is that he is an extremely smart person, with a very strong ability to absorb information, process it and ask pointed question. He also has a strong drive to figure out aspects that he is not familiar with. During briefings, his questions were tough not in a "here is what you did wrong" way, but in a "help me think about this" way. He was always trying to figure out where the unseen problems were that he had not yet notice.
What is needed for the Treasury at this stage is someone who can handle a complex issue, interact with his counterparts abroad, be flexible with a changing environment, and - last but not least - do not let his dealin with Wall Street make him forget that he works for the taxpayer. Tim Geithner scores well on all counts. The only tricky aspect I see is who is going to replace him in NY.