I've run an Eon steel for 5 year, diving in the bright sun of the Middle East, I've not had a screen protector on for a year or so - because I keep forgetting to order them when I go back to the UK. The Screen protector doesn't reduce any glare.
The Eon, does have the widest viewing angle or any of the computers in its class, but yes altering teh position on your wrist will improve things the most.. I also wear mine on teh inner part of teh wrist, so I can see it at a glance and don't need to turn my wrist.
By comparison, I also dive with a Perdix, and that really does suffer from glare and has a poor viewing angle. But both when "properly" positioned are easily readable near or at the surface, and of course are fine in low vis or dark conditions
I also have mine at max brightness.