Yea dude, that window is TIGHT. I've honestly just given up on the WD off double jump method. Besides, edge cancelling an aerial looks more badass anyway. I don't think it gives you anymore height, I think it's kind of like Upke said, it's just more visually sound: when your dair hits the stage, press y. I'm getting pretty consistent with it now too, which is nice... but only on the right side of the stage at the moment.
I truly believe that this recovery could really change up your edge game if used properly (and not overused, just like anything else) and get yourself out of edge pressure. If your opponent is one of those players who sits on the platform and then waits for you to get up so he can attack you (which is SO annoying, I always end up throwing up my shield and getting pressured that way), this can solve that problem. I mean, look at hax on the ledge. He rarely gets punished for being on the ledge.
I also end up throwing my shield and just standing on the platform a lot too, Dave. Lol everything has to be literally 100% perfect if you want to do this.
... Man I wanna play melee now...