I installed the plastic front sill protectors on the rear door sills to protect the paint from my 135 pound dog's toenails.
For appearance, I would suggest some of the billet or chrome sill protector kits. The one's with the flame cutouts look nice (but would have made my problem worse).
http://www.nwdesign.us/PTCruiser_Parts.htm
2003 Almond GT