Yes I use it, it usually works for me but every so often I get a pack that won't set. It could be due to the humidity as that has been high the last couple of days and setting issues also happen more often in the summer. I never had an issue in NZ, only here.
Sometimes if you leave it longer than the 8 hours, it will set. I've also got it to set by replacing the hot water and leaving it for longer.
You could try emailing the distributor and getting them to replace the packets that don't set.