If anything, it's a loss. Tenet hung around too long, and when he finally left, Bush wasn't seen pushing him out the door. Sure, Bush is a loyal guy. But a boss has to fire people. If you can't handle that, the top job isn't for you.
Obviously, the big name being touted to run the CIA is Giuliani. He's probably do a fine job, but I wouldn't want him working for me. He's a hero, yes; he's also a prickly, maneuvering Machiavellian. (Just ask George Pataki what it was like dealing with Rudy -- and Pataki is a liberal Republican like Giuliani, by god. And, as we are told all the time, Dubya is the super, ultra, extra-strength, jackbooted fascist kind of conservative.)
He's just not great cabinet material, I think.