Flyscreen will allow you to unlock using the menu button.
my preferred method is to slide the keyboard open to turn the display back on. if the display goes black while the keyboard is open, any key will turn the display back on.
if the display turns off on you and you are able to catch it quick enough, you won't get the lock screen.
I assume the powerbutton is used because it is out of the way and flush with the phone edge, which helps to reduce unintentional screen activation and save battery life. My only complaint about having to hit the power button is while its plugged in to the car AUX port. If I want to change songs, I have to maneuver my thumb to hit the button, then swipe, then change toonz - all while driving. I decided it wasn't safe and just a pain in the @$$ so now I just set the screen not to shut off at all when I listen to tunes in the car [GREAT BATTERY by the way]. One of the app developers could develop display profiles widget for the Droid like on the (blackberry (for sound) that applies to the display time-outs, with a bit more control.
All that and it's a phone too!!!!