We have quite a lot of Gutermann thread. My wife has so much thread it boggles the mind. Some of my machines have broken the Gutermann thread others love it. That was quite a while ago and I think I've pretty much gotten them sorted out now.
I does do the job I guess but I've found it to be somewhat weaker than a standard size 50 thread of yore. Since most of our machines are "vintage", "classics" and or "antiques" size 50 is what they were probably use for in their day.
The Gutermann size 50 seems thinner than the old American size 50. Perhaps the way they are measured.
Joe