Salifert had problems with the Alkalinity test kit, but as far as I know that was the only kit that had widespread problems (though my kits have not had problems), but the problems were so widespread that it made their customer support disappear, which in turn made them sound a lot worse, and they've actually been slowly slipping off shelves where I've seen them.
I've had good luck with their phosphate kit (as well as a phosphate kit can do it, photometer is much better, but much more expensive).