I never have thought to fret over using any type of sewing thread in my machine. It works or it doesn't is my thinking.
I have lots of Guttermann thread. When Hancock Fabric store closed the last day all the thread was 10 spools for $1!!! No matter the brand or the size. The other customers were all at the C&C and serger racks (clothes sewers). I hit the Guttermann and Sulky racks. I bought every spool left. The manager said he wasn't counting all those spools and I got it for pennies a spool. I thought what in the world was I thinking buying all that thread? But it has saved me hundreds of dollars. I use the Sulky and Guttermann for secret pal and gifts to sewing friends during the year. They think I spent too much! LOL I love the Guttermann colors and so far it has sewn great in all my machines.
I only buy Aurifil or Genziana (same thing) thread here:
http://www.tristan.bc.ca/cart/home.php?cat=36