I have tried Expert Shield Screen Protector bought on eBay from dxcoolguy. It seems to be an excellent adhesive-free product. The problem lies in my own cackhandness in fitting it. I just can't get rid of trapped air and dust.

So much so that my inclination is to avoid the hassle and use the screen unprotected, after all Nokia would provide protection if it was strictly necessary. My Sharp Zaurus screen has lasted several years scratch free although the N800 screen does get more use.

eCloths do a great job of gentle chemical free cleaning.

Does anyone know anything about DuraSec NanoTec?
http://www.durasec.com/catalog/index.php?language=en

The impression I have is that its affect is akin to Armor-All vinyl protector and conditioner (for you car & m/cycle buffs). The web site info is restricted to "This type of display sealing offers an optimal dirt protection (lotus leaf effect), a light scratch protection, raises the contrast and reduces the reflection-effect considerably."

I suppose the real question is, how to remove it if you want to.