I get used to them really quickly, in fact I find them somewhat more natural, but I have big hands, so my thumb cover all the three button at once, and since the volumes ones are highter, it matches really well the curve of the thumb and are really distinctive from the power one, just have to press with the top or the bottom of my thumb to control volum, and with the center to power on/off. Well, just how I feel them. I like them, probably because the location is better to reach them one handed than the ones on the L1520. But I don't like the aluminium material, that's really cheap.
Regardng the onscreen button, I really often hit them accidentally ><