I've always thought a lot of his decisions and the direction he took the NSA, and I think he'll make an excellent head for the CIA. Whether the CIA embraces him, or whether they give him the Porter Goss Memorial Heisman (aka stiff-arm) remains to be seen.
One thing that I've known about for years relating to Hayden but haven't heard it come up at all is the whole Captain Amerika episode. It's pretty tawdry stuff, and there were a number of legal actions related to it - I don't know enough to separate the wheat from the chaff on this one, but I know a few people from the timeframe in question that generally support the story. I'm very surprised the tabloid media (print & TV) hasn't picked up on this. I'll let people judge for themselves:
http://www.capt-amerika.com/capt_amerika_intro.htm
The website is a major character assassination, but it also seriously implicated Hayden in some wrongdoing. Again, tough to judge the merit (or lack thereof) of the charges, but if nothing else makes for some fairly interesting Peyton-Place reading...