I'm still looking at the code trying to figure out an alternative.
Yeah, I think I can make 0 and 00 behave differently.
Now to find a (Adobe) UI designer and see if they agree....
Shift 0 sets Fill opacity to 100 (as with shift any number). So it can't be that. I really think that it should be 00 to make it consistent with the behavior of 01 = 1 and 1 = 10.
In the meantime, if you use Keyboard maestro I have an AppleScript that lets you set both fill opacity and layer opacity to 0, then you can assign whatever shortcut you want to it. I use the period key on numpad (and shift period for fill), but I wouldn't recommend that as a default.
Only reason I don't have it as 00 is because keyboard maestro doesn't support double key press as a trigger.
Chris, why is it always the most used application (Ps) that needs to relinquish its historical shortcuts in favor of the ones of the other apps, and not letting the users decide what set of shortcuts they want to use? Bridge could be the central location for that choice, as it was the case for Color Management.
HInt from Heloise: I have found the period a great shortcut key for "print size." Assign it in the "keyboard shortcuts." (PC here) Crt+0, Crt+Alt+0, and now Crt+. put my popular zooms all in one easy location.
Double zeros is one of the best ideas yet. Makes perfect sense with the current numerical setup for percentages. Hit 0 once, 100%, hit 0 twice 0%, perfect toggle between the two extremes.