This set appealed to me because a) you can never have enough Stormtroopers and 2) I already had the Shadow Trooper figures in the closet so why not in Lego too? Travis sent me the Shadow Troopers from JediCon a few years ago and I’ve never taken them out of the box. (Better investment than a 401k.) The Lego version will not suffer the same fate is not only out of the box but fully assembled. Great small set and a couple of unique figures.
What is a Shadow Trooper (or Shadowtrooper per Wookiepedia)? This is the best answer I found. Maybe there will be more on them in the future movies.