Ok... my opinion being clear on the "stay on focus, it's the tablet I really want" matter, let's get back in topic.
The only one feature that I would require to a screen protector would be some "magic" to allow putting it in place without leaving any bubble behind. So far I never managed to put on a protector without leaving some bubble (which is why I don't use them), but maybe it was just cheap screen protectors on my side.
If they really are going to deliver the Eve with a screen protector, the best "feature" would then be receiving it directly with the protector screen installed, so I won't risk throwing everything around the room in anger because of the bubbles. This in particular as the task of putting a screen protector on is even more difficult on tablets.
Anyway, as the screen has some anti-reflection capabilities, I'd say the screen protector would need to preserve such capability.
An oleophobic coating to prevent fingerprints is definitely a "must have".
I also tend to prefer glass, glossy screen protectors when I see them but that doesn't really work well outside or when it comes to reflections.