I've got one of the powerfast "strap guns" as they call it. I guess they want to distinguish themselves from the Arrow gun for NM that fires bare metal staples.
The powerfast is indeed very fast. It's not a one-hand tool; you usually have to brace the head of the gun with one hand to get the staple driven in fully.
The gun has done about two houses and seems to be holding up. I like the fact that the staple "follower" is attached; all the harder to drop off a ladder (or lose in chopped FG insulation in an attic doing old work).
You still have to carry staples and a hammer, as the gun won't handle round cable (14/3, 12/3).
If anyone gets the clipster, please give us a review.