Good to know feline fanatic! I have a rainbow of colors of poly threads for embroidering and sometimes if I don't have the right color for something I'm quilting I'll be like "oh that's the perfect color if only it were cotton." May have to dip my toes in these new waters.
Going back to the OP, I have bought tons of prewound poly bobbins off ebay for my embroidery and have yet to be disappointed. Having said that, I bought only black and whites in bulk .