I'll reiterate my earlier doubts about porting these virtual buttons and the how dubious I am about it actually being of any benefit compared to what we already have.
IMO, we either will be losing screen real estate or will be forced into more screen taps than today. Either way I see no improvement at all over what we have now, and almost definitely a detriment. At the VERY BEST, with a perfect implementation, it will be a push IMO.
Either the virtual buttons will or will not disappear in certain situations:
(a) They disappear when apps are open. In this scenario, we now need 2 taps of the screen (or 1 gesture area tap and 1 screen tap) to hit the "back" or "home" buttons. Now we need only 1. This is a DETRIMENT, not an improvement in any way.
(b) The buttons do not disappear. In this scenario, we nee only 1 tap (exactly like we already have now) but we lose screen real estate and would seem to gain no opportunity to make the phones smaller, as any given screen size would be reduced by the room needed for the virtual buttons. i.e. that same space is now being used for actual buttons, thus there would be no space savings for the phone.
Still, I am intrigued and excited by the change. I would just caution everyone who blindly sees these virtual buttons as an improvement, to wait and see in real life use just how beneficial they actually are.
On tablets, this is an awesome implementation. There is room for this type of UI. On phones, with smaller screen areas, there are inevitable trade-offs IMO ...