Interesting info here ... one thing I found at a recent gig is that an overcast day, i.e. lots of white clouds, was actually *worse* than sunlight ... it was like having a sky-sized white light all above you! A strategically placed patio umbrella was put into place and made the screen usable albeit still fairly hard to see. I know this is a problem with anything with a screen - my iPad seems to do somewhat better than my Genos, although I can tilt my music stand to get the best angle on the iPad ...
Jim