my new 600 has been having problems with fading under direct sunlight. I called sony customer care (online) and the person there said it is normal under strong sunlight and humid areas. Now I live in Guam so here the sun can get pretty harsh - enough to give you a tan in an hour. However today has not been that hot and when I tried to read on the beach it was a no go. nothing on the screen at all except some annotations (dunno why but annotations seems to be ok. I suppose because they are in general darker)
I know somehave similar problems with fading and some don't. It would be nice to see a poll where people can try out and report how their screen behaves so we can get an idea of how prevalent these so called defective screens are. Also might be good in those times when talking to customer service and pointing out that fading is not normal!
Hope you can contribute and let us all know how bad the problem is!