Looks like I'm the odd one on this subject. I use Connecting Threads 100% cotton (large cones) for piecing, mostly grey, and then I use Superior's Bottom Line in the bobbin. Usually a cream or grey. I'm mixing a 50 wt & 60 wt thread and it helps make for perfect 1/4" seams. On my longarm I just love Glide Thread, but I'm sure it would work just as well for piecing.