While the screw itself seems to be performing just fine I have found the sling attachment quite disappointing, mostly because of how the black plastic ring is rather tightly fitting the screw tube. This causes two issues:
First, the crank arm is freely wiggling on the screw tube, not staying strictly perpendicular, so it tends to catch on the bulge where the sling is attached to the ring. (You can even see this happening on Grivel's own promotion video clip.) If the ring was loose then this would not be happening nearly as much.
The other problem is that if the sling is either completely unweighted or the direction of any pulling force is not perpendicular to the screw tube then the ring tends to lock up on the screw tube. (This is easy to demonstrate by trying to turn the screw while pulling mildly on the sling at 45-60 degrees away from the screw.)
Both issues cause the ring to turn with the screw, as opposed to spinning freely, ultimately winding the sling (and the carabiner, and the rope) onto the screw tube like a winch. A frustrating experience.
You can skip the main touted benefit of the integrated sling and treat Speedy like a regular screw by not having the rope attached when placing or removing it, which means that the sling with the carabiner are now "just" rotating around, without any winding effect. The only remaining value of Speedy is then the weight saving over a traditional quickdraw setup, which I am not sure is worth the extra cost.