To me, they grew on me quickly with my Nexus. Prior to that though, I had the Thunderbolt and Fascinate, both of which didn't have physical buttons either. But, they weren't on the screen real-estate either, so it was half-way there. The nice part of them being on screen, is that they can disappear either via apps, or during certain activities that give you the full screen, as opposed to part of the phone being saved for them.
They have grown on me, and I'm actually not one who likes to have them hidden all the time. I miss having it transparent behind them, but that's probably just a matter of time before ROMs and launchers support that on this phone. And what a bunch of people do, is hide the buttons, and use gestures instead to launch things. That way they get the full 5.2 out of the screen.
I'd suggest going and playing with one for a while in person. Do a bunch of different things, open different apps, watch full screen videos, do a wide variety of activities. Give yourself some honest time with it though, not just three minutes and go "nope". Give a good chunk to it, and see for yourself
