Yeah, I have the nightingale armor. There's actually another armor you get by doing the the little thief missions for vex and devlin. It's called the "Guild Masters Armor". It supposed to be better version of the thief armor, and look different too. It has A LOT of prerequisites which include, completing the main storyline for the guild, doing 5 of those mission in 5 of the cities, and then 4 special missions given by devlin after those 5 in the cities are done.