Silk thread for quilting is not only expensive, it is hard to come by in my neck of the woods.
When Gina Perkes (episode 308) stated she used BottomLine in her long arm machine quilting, I thought I'd give it a try in my Bernina 630. I bought a supply of BottomLine in one of my big orders from the USA and I have used it as bobbin thread in my quilting and embroidery but never as the top thread. Wow, I used it free motion, with the walking foot, and with the embroidery module to do quilting. Love it.
It melted into the ditch stitching as well. Give it a try.