The closer your hands are to your waist, the easiest it is to carry a rig for long hours, I've done it, and I've also carried a light steadicam setup for almost an entire wedding many times and I would choose handheld any moment.
I would try to fit one of these gimbals into a shoulder rig with long handles for those moments where there's not much action and the use the top handle for the fast action ones.
Anyways, I think in a couple of months we'll see lots of review videos. According to their facebook sites, Defy gimbal is already shipping their smallest rig and Bestady will on mid September.