Wireframing a mobile experience

I've really liked wireframing in OmniGraffle for a few reasons:

* The amazing collection of UI stencils, especially Konigi's
* Super intelligent smart guides. Most Adobe apps didn't have these until the last version or two.
* Good multitouch trackpad support. Pinching, zooming, rotating are all very responsive and appropriate in this app. I don't pick up a mouse anymore

I find that working on a big canvas is the best way for me to wrap my head around the many states and transitions of a mobile site or app. I also color-code my connecting lines: green for smooth transition, black for show/hide or modal, and red for new page, meaning a hard cut or new page load if dealing w/ the web. That last one needs a better name :).