Martin Fields.
At first, I was quite hesitant due to the high price of MF, but once I had it, it is the best around I've ever used.
You want to know how to really compare screen protectors quality? Try playing Bejeweled on your PPC for extended length of time. I mean, around 2-3 hours per day. My friend with Brando have already had this boxy-marks (courtesy of Bejeweled, hehehe... ) on his screen protector, while mine is still as good as new.
Sure, one can always go about using much cheaper screen protectors. I used it before and I can tell you, once it starts giving these scratch marks around the SIP (soft input panel) area, then you'll feel your PPC is ugly,
For me, if the PPC has cost you so high, and the screen is one of the most expensive component, why would you go for a class B screen protectors?