SUV has been great so far. Fuel consumption has been v. good (23.5 mpg avg. so far over 6K miles, 26+ mpg on longer hwy trips - I used to avg. 16.5 mpg with my old Sequoia!). Seats are very comfortable (feel hard at first, but are great on long trips). Ride quality is excellent + acceleration with the diesel is v. good for a large SUV, but be sure to make a cutout if installing non-MB rubber mats, otherwise you will limit the travel of the accelerator pedal! Interior is v. nice (especially with real leather), exterior looks good, except a bit minivan- ish from the rear. So far has been reliable except for a problem with the charging of a secondary battery. Main gripes are with stereo/nav.
Acceleration and fuel consumption with diesel. Ride quality. Interior styling and front end exterior styling. Comfort of heated leather seats. 3rd row seats fold into floor.
Make iPod controllable from Nav screen, not just from steering wheel controls. Make voice-control capable of controlling satellite radio. Improve address input on Nav. More storage (e.g. sunglasses holder). Faster opening rear hatch. Backup camera needs to switch on quicker instead of warning.