The very next day after purchasing my AW/Oyster 35d, I went to a store and bought the thick plastic cover for tables. Nicely cut, taped and covered the back seats.
This was after my sister told me how scratched up her car's leather seats were after using carseats/booster seats.
This helps a lot to keep the seats clean - just wipe the plastic with wet towel (you wouldn't believe the stuff that is on them, which would have been on that oyster leather). I ocasionally take the plastic off to vacuum the leather and treat it, and the plastic looks really scratched. Very glad the scratches are not on the seats.

I highly recommend to covert those seats with plastic, or else they would look like crap in a couple years. Especially black leather.