Well, I have been shooting with one hand tied behind my back
, and I haven't minded too much - but my ISO settings are higher than desired. I have a low weight, (relatively) low-cost autofocus Canon 400mm f/5.6L. I consider it an apprenticeship in learning long lens technique. No doubt I sacrifice some early morning shots on the altar of ISO 6400. I don't know how much better image quality I can get without spending serious money, with or without IS. I have toyed with adapting (Ed Mika) one of the old FD Canon Big Whites, but without the autofocus, there is much less utility as a bird-in-flight lens. The EF 500mm f/4.5 no-IS with autofocus is another possibility, but it is still selling in the over-$3,000.00 range, so not enough of an inducement given I don't have an autofocus-at-f/8 camera that would allow use of a 1.4x teleconverter while maintaining AF. At some point, youbetcha I am going to get IS in a 500mm or 600mm lens.