I've used the primal steps for the last 3 years now. I like them well enough. I still use the original buckle straps that came with them, instead of switching it up to the rope. They can tend to get a little loose on me, but I'm a big dude.. 280. Use the plywood platform with it, but it doesn't want to stay tight to the tree. Maybe the rope mod would help with that.
I have used the knaider on occasion, but after one time of trying the swaider and almost wrecking myself, I decided not to go with that.
And yes, they do tear the snot out of the bark of a tree.