The GS500 is a fine machine for distance. I'm not sure how the belief evolved that small displacement bikes are not good for long distances. I think it is an issue of comfort, but if one is in reasonably fit shape and not oversized for the bike, then a 250 or a 500 can be a great ride.
I will probably pick up a 250 dual-purpose bike next month as I add to my fleet. This will either be a Super Sherpa 250 or an XT250. That way for my further adventures I can easily leave the pavement for the trails. The Mexico roads are great, and more and more riders are now adventuring down there. I will make another ride in Feb 09.