I spent some time tracking down why the control did not display for me. Turns out that in the system module the imagecrop module must have a weight greater than the content module. On installation, it looks like it assumes the weight of CCK is 0, as it installs with a weight of one.

It'd save users debugging time if it looked up the weight of CCK and adjusted the weight accordingly on installation. Also, it'd be nice if a status line was reported via http://api.drupal.org/api/function/hook_requirements/6 if its weight is less than one.