I think there's a huge gap between the OP's "no physical buttons" and "no hardware keyboards".
Me, I disagree with the no physical buttons.. My last 3 phones had physical buttons (and by that I mean home, menu, back.. sometimes even search or camera button!) and I found them extremely usable and useful, much more than capacitive and way more than on-screen buttons. Had a honeycomb tablet and the on-screen buttons really annoyed me, much more than the benefit of having them always at the bottom no matter how I rotated my tablet.
Plus my brain, being human and having evolved in the real world, has spatial memory and knows when things move that things attached to them (ie buttons) move too, and can make the transition pretty easily lol. Maybe that's just me, heck I don't even rotate paper maps when trying to make my way somewhere and always know whether to turn left or right.. Maybe I'm getting old?