I wanted to mention about these modern threads like Glide and So Fine and concerns over heat -- I have none. I have old threads that sure enough did melt -- you even had to watch how hot they got in the drier!
I was happy with Dual Duty as I mentioned, until my friend got a long arm and that was when I first got into different threads for quilting. Her machine couldn't wind a decent bobbin and her Type M bobbin isn't standard around these parts so we started ordering from Superior.
Since then, I've been using it for quilting on my domestic too, and have finished about a year+ of using it as my bobbin thread for piecing, with aurifil cotton on top. Been very happy so far, I press every step of the way with a hot (all the way up to linen sometimes) iron and it doesn't bother the thread in anyway. You can press the iron directly to the thread on the spool (I avoided the actual plastic spool...). Recently I won an auction for a large number of So Fine spools, I'm going to try piecing with it top and bottom both. I already prefer a fairly small needle (10) and use little stitches, think I'll be very happy with it as a top thread.