I asked this on the digital forum as well so please forgive any redundancy.Has anyone had experience with this lens? The weight,size and speed are appealing, but I have heard(not much) mixed reveiws on the DO technology. I am considering it as a replacement for my trusty old 600/f4 that I just sold since I don't want to lug around that much weight anymore. The 300/2.8 IS(had the non IS 8 years ago) is another option or I might just save the money and get the 100-400L zoom, but any feed back on the 400 DO would be greatly appreciated.