In an input text field, the text field's "value" property doesn't seem to change until the user has pressed enter on the virtual keyboard. This means that even if keyup events are triggered (see bug 763201), JS won't be able to see what the user has typed so far. I can submit a test case if it's determined that this bug isn't a duplicate.
Is this a regression? You testing on Nightly or Beta?
Works for me, using: http://people.mozilla.org/~mwargers/tests/forms/textinput/inputvalue_typing.html Tested on the Galaxy Nexus, Galaxy SII and HTC Desire HD. Please provide an url or testcase that shows the issue.
Sorry, this is totally my bad--closing this as invalid. Sorry for wasting your time!
By the way, I've just filed bug 764817, which is what I was actually experiencing when I mistakenly filed this bug. (I thought the input value wasn't being updated as the user typed, but in fact it's the case that changing an input field's value during touchstart seems to result in very odd behavior.)