Easily swallows my 350D, 70-200 f4, 17-40, 10-22, 60-macro, convertor, extenders, 580EX, dozen filters, ball-head, panorama adapters etc.
Sewed on a couple of bungee cords for my monopod, down the side, so I can still access the interior. Modified some of the partitions too. So I guess it can still be improved.
Holds all that I need for a days lightweight walk. It would be another story in the winter though.