I bought one of these mostly out of curiosity, because it was so inexpensive. It does work, and surprisingly well.
Warning though... you DO get what you pay for, and maybe a little more. It's not a nice rugged well-built metal rig like you might get from Redrock or Zacuto, but those are several hundred bucks and this one costs almost nothing. It's just made out of heat-bent PVC electrical conduit and an electrical junction box with a threaded bolt through it and some foam grips on the ends. It probably has about $8 worth of parts in it, if that... you're basically paying someone else to design it and put it together, not for the materials. But it DOES work and is extremely lightweight.
I do little extended handheld work... but when I do with my XLH1 I almost always use a P+S Technik lens converter which has an additional handgrip on it so I usually don't need the shoulder brace. But on a few occasions when I've used the stock lens I have popped the SpiderBrace on and it worked just fine. With the XLH1 though I removed the brace's "back tail" (just unscrew it and toss it) because I simply didn't need it... and just used the shoulder pad on the camera. So basically now it's just a set of arms with handgrips and a mounting screw. It does work, though.
Fantastic Plastic Entertainment, Inc. fantasticplastic.com