I have used these recently (12 and 8 ply) for hand quilting woven Japanese fabrics. I love them but... they do unravel and break sometimes, compared to the DMC 8 ply.
I was searching for 'best thread to hand quilt liberty' and came across this blog post that is quite damning of them.
So I am now wary. Maybe ok for wall hangings but I won't use them again for utility quilts.