This is my new favorite thread at the shop! I've been using it exclusively for my tying in the past six months or so! Originally I used Veevus Power Thread for all my intruder flies and always liked its durability. I can definitely say that the GSP 100D is stronger and thinner than the 140 Power Thread. Right now I'm currently using GSP 50D as my primary thread on all my intruder and larger spey flies. For my smaller spey patterns I prefer the 30D. This thread is just exceptional; it's super thin and really strong!
I will say that if you are spinning materials in a dubbing loop, I believe you will need dubbing wax for this GSP thread. It just doesn't grab on to certain materials like other threads because it is so flat and smooth. With a little practice, you can make it work without any hiccups and I think you'll really appreciate how small it is and how easily you can avoid building up bulky heads with this thread.