I received a pair several months ago to "test drive." They're about 1/2 size too big, so I don't know if that changes anything, but I've been using them just on the treadmill. I walk about 30-45 minutes, and the first couple days I didn't feel anything except my knee bugging me (but it's quirky anyway). They did take some getting used to.
I guess walking on the treadmill is a different experience than walking around the parks (not just because it's WAY less fun, lol!), but they're comfortable enough that I'd consider it. Don't know how much toning they really do, but once you get used to the weird way they feel when you walk, they're not terribly uncomfortable.