Over the years, I've used screen protectors from Boxwave, Zagg, Phantom Skinz, Screen Guardz, and Best Skins Ever.
I have been using the Clarivue screen protector on my Evo. (clarivue.com) The screen protectors from Clarivue are as good as any I have used (and much better than the Zagg or the BSE protectors). They are a dry-apply type with no glue. The surface feels smooth and just like the regular screen. Clarivue comes with a lifetime warranty (which I have used). I like these the best because they are easier to apply than many other brands. (instructions on Clarivue's site).
The trick to getting a perfect installation is to use 2 pieces of scotch tape to get rid of any dust particles stuck under the protector. One piece to life up the corner of the protector, another piece to suck up the dust particle.
They have just become available for the Optimus S. $12.99 for a 2-pack, free shipping. 10-percent off coupon is: protect331
I just ordered some for my daughter's Optimus S phone for her Christmas present. I'll keep buying Clarivue until I find something better.