The 2008 models are a RWD GS 460, RWD GS 350 and AWD GS 350. Here is an excerpt from the Lexus website:
342-hp V8 (GS 460)
With a 342-horsepower [1], 4.6-liter V8 engine as well as direct and port injection, the GS 460 can go from 0 to 60 in a mere 5.4 seconds
So, they upped the model from the 4.3 liter to 4.6 liter engine.
sk31 - I can't speak for the ride of the 460 model as I have not driven it, but as for the GS exterior, I think it is a beautiful look. The lines are great, it has nice flair...and...if you ask me...it looks mean in the rear view mirror. I have had 3 Lexus automobiles and always go to the dealership for services. They seem to charge a fair price compared to other vehicles I have owned. In fact, because they suggest service work every 5000 miles instead of 3000, I believe they charge less in the long run.
The GS came out in it's current form in 2006. It had a completely different body style from 1998 (I believe) until 2005.
$65k is a big chunk of change, but, if you compare to a BMW 535xi twin turbo, it is approximately the same, and has more horsepower.
Hope that helps with your decision.
--Duckman