The Hype about the extenders may turn out to be a disappointing. Since I would never consider buying this lens, I thought the review on the 400mm would be a good indicator of how much hype vs reality we were really getting out of Canon on the new Super Tele's.
Originally Posted by Daniel Browning
I think also if you can hand hold the 400mm easier now, and since I do allot of shots with my 500mm hand held, the new 4 stop improved IS system may turn out to be the best advancement.
When the 500mm II comes out I think it will be worth the upgrade just to loose the pound and a half and can get a better IS system and I will still go for it just for those reasons.
Eventually I would like to see a review of the IS system on these lenses.