Having owned my RX400H now for over a year, I can say that is a fantastic vehicle to own and drive. I drive over 1000 miles a month and average 24-28 miles per gallon. If you don't get this type of mileage, you are not driving it the proper way. It took me over a month to get used to the subtle changes you need to make to maximize your fuel economy. It is so quiet for an SUV and very comfortable. Whether I am alone, with my grandchildren, or my parents, everyone raves about the comfort of the ride.
I don't really have one, but my grandchildren love the integrated Bluetooth phone to talk to their grandfather or parents. My kids like the nav system.
The nav system needs to allow the passenger to change things while the vehicle is in motion. Add option of air-conditioned seats (like my husband's Lexus has) for those of us in a warm climate.