Found this brief review of the GS500 on an Australian web site if anyone is interested..

http://bikepoint.ninemsn.com.au/portal/alias__bikepointau/tabID__5760/BikeArticleID__119521/DesktopDefault.aspx

I'll second that.  I've just got home from a 400km trip.  4 1/2 hours in the saddle, 120-130 km/hr most of the open stuff, some really good tight bits (http://www.targa.org.au/images/maps/2004legmaps/day2.pdf).
On this map I went from Launceston to Hobart via St Marys, Elephant Pass, and down the coast.  Elephant Pass is great.  Really tight, narrow (two cars will only just pass; bus? Forget it!), good surface but a bit choppy in places.  Similarly, from Triabunna to Hobart- 75 km of winding mountain road, a bit wider to accommodate the log trucks.
The bike never missed a beat all day, and the overall fuel consumption was 20.6 km/l.  Staying below 5,500 rpm, I usually get 22 km/l.