I've been playing around with the 1.5mm zline for my guylines and find that it holds adjustable grip hitches quite well. My only issue is that ti's really hard to cleanly melt the ends to prevent fraying. I've ended up tying double over-hand knots and trimming the cord about 1/8 or so past that, and just letting that much of it fray. For the most part, once I've tied the knots in my guyline, I don't really have much need to untie them anymore anyway. It's a bit stiff though when you first get it, like solid core copper wire, but it softens up with use.
I've also used the 1.25mm stuff with cordlocks for stuff sacks, and that works really well for that.