Being the damn fool gear collector I am, I ended up with a 2xIII about 6 months ago ($350 Craigslist deal I couldn't pass up). Honestly though, it's sharp but not worth the hype. At least on my 500/4 I couldn't see any real difference between it and the 2xII. Maybe on one of the new mkII superteles the enhanced AF would make it worthwhile, but for ordinary mortals with older glass I'd give it a pass.
PS. About that new Gitzo birdwatching head - No matter how smooth the movements the center of rotation still appears to be well below the center of mass. For a big lens it's hard to beat a good gimbal head like the Wimberley...
Last edited by vachss; 08-13-2012 at 07:58 PM.