I did a lot of searching and reading on these things before I bought into them...most people (and reviewers) report that they like the Boxwave stuff, but that it was a pain in the you know what to install due to the fact that it slips under the screen, its thick, and that you have to bend it to install and can damage it while you do that.
After reading that I went with the Pocket PC Techs - WriteSHIELD C2 screen protectors. I got them in on Tuesday and I could not be more happy with them. They cost a bit more than the others, but they are I would say 98% optically pure...meaning all of the colors and the brilliance from my X50v come right through.
You can find them here:
http://www.pocketpctechs.com/