I've been steadily progressing with my Sarah Fielke Simple Folk quilt. The animals are so enjoyable to sew. I usually use Aurifil 50wt for applique; I have so many colours that I can nearly always colour match and I found the stitches were hardly visible. I do have one or two reels of 80wt thread from retreat goodie bags and although I've tried this lighter weight for piecing (which didn't work out), I hadn't tried it for applique and the grey seemed like a good match. It was amazing, invisible stitches even at the V areas around the feet where there are many extra stitches to compensate for fraying fabric.
It's hard to see the difference but you can feel it as you stitch. For hand piecing, I found the thread just didn't hold up to the pulling, especially loading several stitches onto a needle at once. But, for applique it's a game changer for me. I only have three colours of 80wt so I'm planning some future additions. As it's so lightweight, there's so much thread on each bobbin (274 metres) that it would take forever to finish one so it seems like a soound investment for future applique! I used it with a size 11 Jeana Kimball straw needle, very fine, and it flowed through the fabric with no knots or tangles.