everywhere you go there are going to be stupid people. Pacelines on an mup don't make sense because if you're going the speed limit you're going too slow to get any benefit of drafting. Sometimes I go fast on the MUP on my commute, but only in regions when the only other people in sight are other bike commuters like myself and there's limited access (one stretch has a fence on one side followed by a river and the other side has a fence and limited access highway. If no one's around and I'm in a rush to get home I'll up the tempo there. Other stretches, MUP's can be nicer than the roads (and have better scenery - and not just sunbathers) so if I'm out for a leisurely ride, I'll take them where they're better and less populated and roads when they're superior. It's all about knowing what's best for the situation. I also like them for exploring new areas because you can't get too lost (though sometimes getting lost can be fun and a good way to explore an area - in new places I've taken a map with me, planning not to use it unless I absolutely had to and set out to get myself lost with the hopes of getting home again in 20 or so miles). But then I'm not a racer so I just ride however I'm feeling when I'm feeling it.
__________________
Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"