say you have hundreds of templates to enable all of them. you wouldn't want to click "yes" radio buttons over and over again for each every theme. I suggest to WPMU dev team to add a feature like "enable all themes" for this kind of scenarios.
anyway, my workaround here is to use javascript + firebug, and also took advantage of having jQuery on it.
to enable all:
jQuery('input[id^=enabled]').each(function(){this.checked = true})
and of course, to disable all:
jQuery('input[id^=disabled]').each(function(){this.checked = true})
you can run this via your firebug console. or you don't have firebug, you can run it directly to your browser's address bar using javascript: protocol and adding void(0) to the end.
e.g.
javascript:jQuery('input[id^=disabled]').each(function(){this.checked = true});void(0);