In no particular order in addition to above:

-seals around the two tailgate windows, make sure not leaking and no corrosion inside or out
-climate control filter, make sure it's clean (and not the original one) or look to replace the climate control fan
-climate control fan, make sure it does not squeak while running on auto for long periods of time
-radiator neck thing not the original plastic
-runs at the right temperature
-transmission shifts smoothly from park to drive, etc
-breaks smooth, i.e... rotors not warped and calipers good
-cruise control functions perfectly, what's the name of that $1,000 part that controls this?
-back wiper and squirter, check back squirter reservoir not leaking
-all idiot lights light up (and then go out properly), same for interior lights, especially the four in the tailgate
-bouncing speedometer
-tailgate close-assist works
-struts that push up and hold the tailgate
-If you want the cargo cover/partition net, make sure the car comes with it
-all seats (front, middle, and tailgate) fold up and down properly, there's a section in the owners manual that shows you.
-three headrests across the back that all come out the way they should
-all the speakers working

Fantastic wagon. So smart and easy to drive. GREAT kid vehicle. My wife and I love ours.

__________________
Michael

1988 300 SL (5 Speed)
1994 E320 Wagon
1997 C230