Did you not just say whether they can punish you for it is matchup dependent? It sounds like you're assuming you get punished in every situation.
The punish you are dealt with is dependent on the movespeed. The situation it leaves you at is always worse than if you had just walked/ran. (Except you just did 2%, whoppie?)
As I said this technique has some uses and we will probably find more but "mobility" isn't one of those uses. There's a clear cut winner between this and running/walking.
Your second post makes no sense as I am comparing 2 actions. Running/Walking and doing this to "slide backwards", if something else is discovered in the future that cuts all lag from this technique or to allow yourself to slide much greater length then another comparison can be done then.
For what we know of the technique as of now: It's slower than running/walking, puts you in enough lag to be punished by characters with a decent runspeed (most characters in the roster) and even if you manage to push your opponent back with this technique while using it as a dash he will still be able to reach exactly where he was from you (distance wise) before you come out of lag.
I myself have used this ability to push people away from their attack range (push a Marth who'se about to Forward-Smash), that way he misses his attack and I can go in with a punish. That's a great use. I can see it being used on the edge to lift people up slightly to land F-Airs or F-Smashes/U-Smashes. As a "dash" it's not useful.
Also just so you know. If you really want to space out an opponent: You can just short hop and Up-B into the ground. It's essentially EXACTLY this, only it makes you slide much farther and it also pushes your opponent much farther away.
And for future reference. Yes, it is expected of you to wake up and actually read what people write before commenting on things you haven't even read. It's funny you say "don't understand me" when you didn't even understand at all the first 2 posts I quote, you didn't even know what they said.