One of the joys of the F5.6 is its relative small size and weight. Compared to the 400mm F4 for example it looks almost like a toy. Indeed Arthur Morris called it his toy lens but produced amazing results with it. If you want to carry it in the field for any length of time you will appreciate its lightness. If you can hand hold it steadily this will offset the lack of IS. My wife is not a regular photographer but used it on safari in Kenya and found it very manageable. IS is not a direct substitute for good technique!
