PSummer 2011 my husband and I rode from Breckenridge, Colorado to Fallbrook, California. He on our Sports City 250 and me on my BV 500. The Sports City held 85 mph on I-15 for 150 miles in 112f heat with a couple of stops so WE could cool off and down some water. Before that trip the Sports City spent 2 years running up and down the Rockies from Denver to Breckenridge. Yes, it did slow down on a few of the grades but it held speeds equal to that the 4 cyl cars on the same roads.
Max speed he rode was 88mph by gps. Max speed on my Vespa GTS 250 is 82-84 by gps which has been ridden on I-10 in Texas though I prefer secondary roads to freeways even on the 500 which will cruise all day long at 85, even 95 mph (though gas mileage sucks at those speeds) which is the speeds I crossed most of Nevada on the way back from California after leaving the Sports City with my son.
Reputable 250s are quite capable of 200 mile freeway trips unlike some of the low end Chinese ones. We've got some folks who ride no name Chinese "300cc" scoots that can't keep up with our Buddy 125. my husband's ridden it on the freeway at 65mph but I think its too light for freeway traffic. A friend has told me that he cruised all around So. California from Costa Mesa to San Diego to Big Bear 2 up on a BV 350 and never felt like he was low on power. Knowing Chris I'm sure he spent time on the freeways especially since he said he cruised 2 up at 75 for a couple of hours.
Photos from that trip are on my blog starting at http://cheryldwise.com/?p=164