The 600mm shrinks

I've carried the Canon 500mm f4L-IS in preference to the bigger/heavier/more expensive 600mm telephoto for some time. I use it in Central Park and like it in particular for its short minimum focus distance. Now Canon have formally announced the successor to both the 500mm and 600mm supertelephotos:

http://www.dpreview.com/news/1102/11020709canon500mm600mm.asp

and the first thing I noticed is what I suspected might happen - the new 600mm has become as light as the old 500mm and has the same minimum focus distances as the old 500mm. Of course this new 600mm will be very expensive for a while even after it hits the streets, but it is going to be a very attractive lens. In the meanwhile I think I'll try using the 800mm plus extension tubes and see how that goes, although the 800mm will be too large a magnification for some of the bigger species of birds at it's minimum focus distance.

Spec for the old 500mm is here:
http://www.usa.canon.com/cusa/consumer/products/cameras/ef_lens_lineup/ef_500mm_f_4l_is_usm#Specifications