Hey TiggerTwo,
The best long distance ride report was written by a member called Crudmop last year. He did 5000 miles in ten days. You can see the thread here
Long Distance Touring
In the very last posting on that thread he posted the url for his website which has a detailed report and lots of great photos. Well worth a read.
I tour on every bike I've ever owned, and the S3 is fine for touring. I've done a few 400 mile days and I find the seat better than many I have had on other bikes. See this thread
Luggage for a discussion about carrying luggage on the S3.
Apart from the Ventura luggage system which I bolt on whenever I am going on a trip, I have not seen the need to make any modifications to make the bike better for touring, apart from adding ZRX Kawasaki mirrors to improve the view behind. Also I have not removed the whole rear fender....(just shortened it a little) as I ride in the rain regularly, and removing the rear fender exposes you to a constant shower of muddy water when the roads are wet.
While it is not in the same league as a BMW K1200LT as a tourer it is great fun when the road gets twisty.