Heres a pic of mine. My screen has 2 little areas on the side of the screen which has the home button on.
When playing games and browsing the net, I can't see it. But when I have a dark background, like a navy blue or black, I can see it, even at 40% (which is what I usually have it at) during the day, and evening with the lights on.
It's slightly visible when watching films, not much though. About 1/2 of each area is covered by the film.
As you can see from the pics, I set the brightness to around 50%. I set it to that because my ipod cam had trouble picking it up.
The 1st pic is an unmodded pic. The 2nd pic I modded in photoshop to get it closer to what it actually looks like.