I thought similarly of the Milton Keynes Sky Ride, where it rolls down to the station and back up. Its no serious gradient (1km @ 2.5% a few bits @ 6% according to strava), but it was enough to have people, especially families with young children walking their bikes up the hill every lap I did. The downhill side wasnt so bad, despite speedy children but it ran into a hairpin turn which people were struggling to slow for and take without riding into eachother as they bunched up, but it seemed okay.
It was hard to judge the MK ride though, because not many people turned out despite what Sky claimed, which in some ways was good, there were no queues at any of the stalls you could get straight onto try the 'bent trikes and silly clown bikes etc they had. Unfortunately they put it on the same weekend as my favourite F1 race, so i cant stay much past midday.