Ideally, let's get scale out of the meta viewport tag.
In testing, one of the devices was zooming when focusing on form controls, then not zooming back on blur. Sorry no detail on which device... :/
As far as I can tell, setting these viewport properties are the only way to keep the zoom at 1.0 during orientation change... hrmmm
Tagged for alpha.
Note: filamentgroup.com (mobile site) does not disable zooming and for some reason, it adjusts fine on orientation change. Maybe worth examining the differences.