Well, we had one Brit on his 1400GTR doing the Iron Butt Challenge in the US recently. It was the only Kawasaki 1400GTR entered out of a start list of 97 bikes. He has written a report in the latest MCN here. Nearly 8000miles in 11 days and not a problem. Bike went brilliantly the whole time. Even had the stock seat which didn't give him any buttache either.

The challenge was won by a guy on a BMWR1200GS with 12,568 miles but the report said that he was lucky enough to be riding one of the BMWs that did not suffer a catastrophic failure.
www.ironbutt.com