HI,
My Gs450h is 2007 and currently only has 25,000 miles, the guy who owned it before me worked out of the country a lot hence very little miles when i got it :)
As for my MPG on the centre console it says 27 to 28 mpg on average, but i drive it in sport & hybrid power mode alot and dont really get to do many long runs or motorway driving as i live in N.Ireland.... when i bought the car in Southampton and drove it to stranraer in scotland to get the ferry back home it was motorway all the way and the best i got was 31 or 32 mpg mid you i was averaging 80 - 90 mph on the motorway...
Other than this i think the car is great, one issue i would have is that mine dosent have the aux port if you wanted to plug in your ipod... it seems to have came in the later models.