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I’ve had trouble with this myself recently (see http://css-tricks.com/forums/discussion/15236/solved-ipad-zoom-problems where I posed the problem initially). After doing a lot of testing, I came to the conclusion that the maximum scale and initial scale and all that wasn’t necessary. The only pages that were zooming in and out (after reloading or rotating) and didn’t show the full width of the page, were those that were still under development.
Once pages had their “finished” structure and some proper content in there, all navigation and resizing and reloading and zooming went all fine — without any use of the meta viewport stuff. Landscape or portrait, every page would just be showing the full width all the time.
I think iPad is pretty smart about this stuff and knows when a page needs to be zoomed in or not, or at least it tries to guess.
Not sure if that applies to your project, but it sure did for mine.