Such a loaded question
, only because there is such a vast number of answers. With my computerized Bernina that I bought off craigslist came about 200 cones of Isacord. So, for the most part I use it. I have recently learned to appreciate Bottomline in my bobbin. Doghousemom probably summed it up best... buy cautiously and experiment before you start laying out lots of $$$ Also, if someone else's quilting has the 'look' I like, I ask them what they used.