Matthew McManamey , Dec 04, 2007; 12:04 a.m.
I have never seen such an animal. Macro photography with tubes or bellows is a very delicate setup and usually requires a tripod or some other type of bench anchor. DoF is so thin when doing this it is EXTREMELY difficult to maintain focus handheld. Stopping down the lens to improve DoF usually gets you to a shutter speed that you can't hand hold either.
The point is, by the time you get everything else set-up, AF is no real advantage. In fact, you'd be more likely to get mad at the AF and turn it off anyway.