The OP of this thread is about a panel for one-eyed "peep-hole" EVFs, not a rear-screen LCD, so there is no more problem with bright sunlight than an OVF.
I would respectfully disagree here.
The older EVF of the Konica Dimage A1 was absolutely unreadable on sunny snow, too dim (had to wait about 15s that my eyes accomodated to the darkness, not very practical for the decisive moment), and my olympus VF2 lacks still a bit of brightness in these conditions (makes the image appear as underexposed when it is not).
Edit : In comparison, the keyhole of the older Olympus C2500L (a true SLR, but the viewfinder was at scale with the tiny sensor) was much more usable than the A1 in even moderate sunlight.
But I may have already had a bias towards grond glasses...