I purchased my 400h in June of 2006. Previously owned a 2000 RX 300 and 2004 RX 330. I've driven the car about 3000 miles and find it to be a completely different car than the previous Lexus models I've owned. So far, getting about 30 mpg with a mix of city/highway driving (my RX 330 got about 21-23 mpg). I live in the mountains and drive up steep grades and around sharp curves and love the handling and performance. Achieving peak mileage in a hybrid requires some adjustments in driving technique, but this doesn't mean slow driving! Fit/finish are better than on the RX 330. I like the navigation system, but it took a bit of time for me to figure out how to work the A/C and airflow.
Handling and performance better than RX 330 or RX 300. The ride is smooth and quiet. Gas mileage better than expected given reviews posted by others. Navigation system, power liftgate and passing power are my favorite features. Compared to RX 330, electronic transmission is awesome!
Heated rear seats. Make the same adjustments available for front passenger as for the driver. Better cupholders. A more commonly available tire size than is currently offered. Hybrid logo on the back of the car. Rear backup sensors. Insurance is more costly for 400h than for 330.