I'm interested in making my panniers a little less "scarred". I read somewhere that if you gently heat plastic parts with a hot gun blower, then the marks can be removed. Anyone ever done this, and...does it work?!!

I have sanded and buffed out scratches on panniers. I started off with medium grade wet and dry using a block and doing long strokes so as not to create a low spot. I progressively used finer wet and dry, and then used a car buff with cutting compound. For the final stage I used the buff with plastic polish, then coated with Forever Black followed by Surf City Black Max. I believe .75 filled and sanded his followed by paint.
Regards Martin.

That sounds like an altogether better idea. I'll give it a try!
Thanks.

I sanded with 220 and 320, coated with adhesion promoter, and used a matte black paint followed by a semi gloss clear coat for wheels.  Both came in rattle cans.  Looks pretty good and if need be can be touched up without too much work.

Duck has his coated with pickup truck bed liner.  Has to be done professionally for best results, but I understand it is tougher than almost anything the panniers will ever come in contact with.