Can't comment on the fit and finish of the aftermarket kits, but the OEM set is a perfect fit and absolutely no grief when it comes to installation. Did my front strip in about an hour including removal of the old one.
Contrary to the service tech, who told me that I would have to remove the entire front bumper clip to remove the old one, I simply unfastened the screws that held the license plate pad and temp sensor, pried one edge of the strip off with a screwdriver, grabbed tightly, and flung the rest off in a whip-like fashion!
www.************************ sells floor mats for your car as well in a variety of colors and custom designs. I plan on getting a set for the rear since my 300E never came with rear mats.