I have the Almond+ and I've been using the ZW078-B/C (EU model) with a water storage tank heater for the past 6 months. It works 99% of the time: 99% of the time it executes the "turn on" command successfully, 90% of the time it executes the "turn off" command successfully. I got it so that I could schedule my water heater to turn on at a certain time and turn off later, so I've needed to add an extra schedule to attempt to turn it off a few hours later just in case it didn't turn off the first time.
In other words, so far it's been working well for me. I only had one scare today when for the first time it refused to communicate with my Almond+ (that's how I found this post). But after rebooting my Almond+, it's working once again.
The only problem is that the energy monitoring has never worked for me. (Not that energy monitoring is well supported on the Almond in the first place).