It could have cost me more...but I have kids. You see, earlier this weel, I'd been having an email discussion with Bryan on TC IQ, and yesterday I had the Canon 2xIII in my B&H cart, along with the Kenko 1.4x and 2x TCs, planning to try them all out head to head. I was planning on using the Kenko 1.4x with the 100-400mm when it was not practically feasible to bring the 600 II, the Canon 2xIII mainly to use with my 70-200 II, but also for Live View AF of static subjects with the 600 II, and probably returning the Kenko 2x if the IQ was too poor (I could only find one review of it with a supertele, reported that AF worked with the 500/4 II but IQ was weak, but with an n=1, I wanted to see for myself).
But like I said, kids. They interrupted my ordering process, my cart timed out, and I figured, well, I'll get to it tomorrow...but I was busy in the morning, then a little bird (species B. Carnathanius) told me to check out the news page in a few minutes.
So, if you think about it differently, the firmware update actually saved me either $259 or $528 (depending on whether or not I would have kept the Kenko 2x).
Thanks, Canon!
Now thats an explanation....
This is a Kenko 2x a few years ago with the 50D and 100-400 just after I bought the lens.
Spring Turkey by hdnitehawk01, on Flickr