There's a hilarious game where pro player Brian Braun-Duin was playing Nadu at a Nerd Rage Games event and presented the combo, but his opponent was just like, "All right, combo off and kill me." And BBD proceeded to spend the next hour seemingly aimlessly looping through his deck
A free Equip cost makes it easy to move this card where it is needed both before and after combat, and in combination with Leonin Shikari, effectively gives all your creatures Shroud
Even though on average you will see two targets when you Impulse with a deck of 2/3rds targets and thus have the same selection potential as Sleight there are several reasons why that is worse
But for some reason it never occurred to me that they could end up going on lands too
An attacking or blocking creature that phases out is removed from combat
All that for just one red mana, which is pretty darn good