I recently tried the Clarivue Anti-Glare screen protector to see how different it is from the Ultra-Clear finish.

And it's very different. In comparison, the Anti-Glare is thinner, less clingy, and a bit easier to install. It enables much more touch-screen sensitivity. It offers a dull / matt finish which provides hardly any stylus resistance. That said I put a fairly long and deep stylus scratch in it within a few hours of use.

The matt finish reduced screen visibility enough to be noticable. It looks like a significant drop in resolution. I had it under incandescent light, fluorescent light, and direct sunlight. The "anti-glare" gains were minimal at best - especially outdoors where it performed particularly badly under direct sun.

Overall I didn't like the Anti-Glare protector very much, and find the Ultra-Clear protector far superior. It too scratches fairly easily, but the clarity is fantastic, and I like the amount of stylus resistance that it offers.

It appears that Clarive is cutting the N900 protectors a little bit smaller which makes them somewhat less tedious to install. Trick is to give the screen a blast of compressed air immediately before lining up the Nokia logo first.