I use omnigraffle on my ipad extensively - I've got about 20 different diagrams, some of which have turned into real-physical things ( a brick walkway pattern,

I use omnigraffle on my ipad extensively - I've got about 20 different diagrams, some of which have turned into real-physical things ( a brick walkway pattern, is one example). It's still about 5x slower for me than a whiteboard or paper napkin + pen, albeit much easier to edit once you've created something.