I'm putting this on the back (on order, Carbon Fiber) since I already have a scratch:
Skinomi TechSkin™ for Asus Tablets - Skinomi TechSkin™ for Asus Transformer Prime
Comes with a screen protector too but I may not use it.
I'm only going to use the back piece since it's the only part that touches when sitting on a table or countertop etc.
I'll get a sleeve eventually but I hate to put it in a case full time. I like the feel of it without anything on it and the thickness is one of the reasons I waited for an Android tablet this thin. I'm not going to use it at work or anything. I see getting some sort of case long term but for now I'll go with the Skinomi and a sleeve.