I wonder how a landscape keyboard would work for an iPhone. Could it be more of an issue than expect.
Not having one, I'm trying to imagine here.
At default, it's natural to hold the phone with your left hand vertically, as it can rest in your palm as you type and use it with your other hand.
At landscape, it becomes a little more awkward. I'd imagine holding it like a PSP and typing with you thumbs. This could be faster and more convenient for long messages or chat.
Otherwise, with normal use, say just finished typing at landscape with thumbs, having to do other functions could be hindered. As one hand with suddenly have to let go to do multi touch functions and such, and you may attempt to hold it with your left hand with the thumb on the screen still, possible hitting a button by mistake.
Then the constant switching between landscape and vertical would increase the change of dropping it. Especially while trying to hold it with the left hand positioned for thumb typing. Is there that much of an improvement to warrant the constant switching between portrait and landscape to be added?
Just a few thoughts. I should be there, but I just thinking of other issues from using two thumbs to type while holding a device that's a huge touch screen and often requires free movement of one hand to do multi touch stuff.