I don't use a screen protctor on my jetBook, or my Kindle 3. I do use screen protectors on my PDAs, where you're writing on the screen with a stylus. I suspect I'd use a protector if I had one of the new Sonys where a stylus can be used.
With respect to Kindle cases, I use a Mead "At-a-glance" planner cover from Staples for $9.99. It has a pocket for the K3 (originally for a notepad) and plenty of room for the charger/cable.
I gave a K2 to my sister for a gift, and got her this case:
http://www.amazon.com/gp/product/B00...indleboards-20
It's less than $12 and is a hard shell. The K3 might be a bit loose, but I can't see what harm that would do.
Regards,
Jack Tingle