I just got a set - well, had them for a bit, but just got the scooter out for the first time. Anyway, I get them adjusted and clasped correctly, I think, and they are popping off while walking. Kind of a pain in the ass having to stop immedaitely so you don't crunch them under your boots. Then when you get on the bike, and bend your knees, the pants get so tight that the jeans on your knees are uncomfortable. If I loosen them up a bit, then they slop around when walking - causing them to fall off again.
I will say that is nice not having your pant leg sliding up your legs when it's in the 40's, but gosh, so far it seems these things are more trouble than they are worth. I was actually thinking a better solution would to put a single snap on the inside of my boots and riding jeans just fitted loosely. As long as the cuff doesn't go over the boot, that's cool.