15-20 depending on load / conditions. Averaged about 17 with a full load including cargo bag on the roof and 2 bikes on back over $500 miles with mountain passes and lots of wind. Can pull 20-22 if you're careful, but probably won't happen with a load or terrain. Drops quick when you mash the throttle though.
Bottomed out a lot even on the highway with a full load in the back. I am going to try some airbags for now, but I think eventually a new suspension will be in the works.