I've used them for the last five years, they're quite common in Sweden. Much of my diving would be classified as very cold water, mine diving with temperatures in the 2-4 degree celsius range throughout the entire dive. I tend to get cold hands easily but the quallofill work out fairly well allowing for 60 minute exposures without issue and about 90 before any significant impairment on function. It's the best combination of manual dexterity and warmth that I've tried. Main negative point is that they're quite fuzzy and occasionally strands from the gloves end up peeking out between the latex seal of the gloves the seal on the suit.
It's in no way a revolution in warmth compared other bulky gloves but if all you've tried are the thin liners that the gloves comes with it's a great improvement.