I've used monofilament on three projects and found that using a "metallic/monofilament" needle really helps. My bobbin is also wound with monofilament. I used the Signature transparent size .004 that Joann's carries. As others have said, because it is invisible it's difficult to see whether you have pokey ends sticking up, so I make sure to cut the tails as soon as I'm a few stitches along the row because I'll never find them again.

I have used YLI and Sew Art monofilament nylon a lot, and have had no troubles with it. I usually use a 70/10 needle, and regular thread in the bobbin. I have used it both for applique, and for quilting. I do plan on buying some of the polyester the next time I need some invisible thread, but am going to use what I have first.

I use to use the monofilament thread. Not always easy to see and keep from getting tangled. With better lighting I may try it again.