Ah. I just 'got' where PiZero's going with his new (beta test version of his) 'Stealth' theme. It's for those nights out when you'd really not advertise your smartphone to the criminal fraternity by its dazzling luminescent display. Or perhaps for surreptitious use in a darkened cinema? Anyway, head on over if you'd like to help test the concept.
Excellent idea! I love it! Some backsides: in calendar the days should be visible, also the clock, as already mentioned.
Sadly, all 3'rd party apps are still visible by icon (resco news, agile messenger, music folder etc).
The profiles should also be visible (you don't want to miss a call just because you're on silent and don't know that).
There is actually an app bundled with many current S60 models which lets you use the phone with your eyes closed, as it uses a special menu system combined with synthesised speech. It's presumably intended for blind people, but I've never seen Nokia actually advertise it at all, or tell anyone about it.