If you're talking about the one that sits on the ground and moves around on a spring...yes I have one and use it.
It seems sturdy enough for now. Though it's designed for targeting and reflex so you're not intended to hit it full power anyway. For me, I use it to practice hitting and moving. It's not fast enough for combinations in it's long-swaying state, one punch will send it flying and out of range for follow up punches. So you're best best for that is to punch it once, move or circle, practice upper body movements like swaying, rolling, ducking, rolling, slipping, etc. Then hit is again, and do the same.
What I do like about it, is the shape of the target, the density of target, and the ability to hit it at different angles more realistically, and that if you punch it incorrectly with the wrong knuckles or without being at the proper alignment it will let you know.