Since the Prime has Gorilla Glass you really don't need a screen protector. It's pretty damn hard to scratch Gorilla Glass.
Its hard to scratch but not impossible. My wife's has had here Samsung Infuse for 3 months (also has Gorilla Glass) and already has a few scratches on the screen. I just don't want to take any chances with the Prime.
Using a Skinomi until SGP release their protectors. The SGP Ultra Fine protectors feel like glass and have great anti fingerprint / glare properties. I emailed SGP ro inquire about their availability for the Prime. Here was the response:
"Hi, my name is Sue from SGPstore.com
We are planning to create our Steinheil Screen protectors for the Asus Transformer Prime.
We don't have an official time when it will be available but probably early 2012."
Sent from my Samsung Galaxy S II