we have had our 2007 RX400H for about 2 months now and love it. going to Adelaide and back the economy is just over 10/100km (we are down on the Fleurieu Peninsula, so have Willunga Hill , the start of Victor Harbor Rd and the start of the Southern Expressway hills to deal with!) but down around the Peninsula we have been showing high 8s low 9s which , for the size of the car, i think is great.
Had it serviced by Lexus of Adelaide (Who were brilliant i have to say) for its 180k km service, and they gave it a clean bill of health which was a real nice thing to hear.
My father has a 2007 RX350, and i really think these RX's are very underrated vehicles