I use So Fine and Bottom Line in the LA.. BL only in bobbin and SF mainly to quilt with unless it matches backing for bobbin. I have never used either of these for piecing. I have used left over BL from the bobbin(LA) to finish binding. I have a friend who used SF for piecing and she said it melted under a hot iron. And to look at her ironing board, she would know! She now uses Aurifil, which I have never used. I can get almost a cone of BL for the cost of a spool of A. I do have some now because M* had a special a few months ago where it averaged out to $7 a spool including shipping. I haven't used it though.
I guess I'm one of the few who does not care for Glide. I own a few cones of it and will use it, but it's not my favorite. My first experience with it was when it first came out and I needed a particular shade of purple that they had and I also needed purple for the bobbin.So I bought the prewounds for the bobbin. I still have more than half of the bobbins and almost a full cone of the other. Now that they make their bobbin thread in 60 wt. I would use it if I could get it locally. I can't find any of the threads I use for LA ing locally. That's why I try to sort of stock up with Superior at the shows.