I have three of the plugs at the moment. They seem to behave very similarly to the Hive Active Plug in that they are marketed to work with a hub, detected by SmartThings as a ‘Thing’ with the same manufacturer, work with the ‘Zigbee Switch Power’ device handler, and the power reported via the device handler is a factor of ten too low. I would imagine the Salus plugs act as Zigbee repeaters as mains powered devices generally do but I have no way of knowing.
One plug is just being used to switch on an awkwardly positioned USB charger when I realise the battery in a bluetooth speaker has gone flat. So it is off most of the time. Another one is being used to switch a fan on and off, with SmartThings acting as a timer, so gets used a bit more at the moment but only with a load of around 25W.
The third plug isn’t being used because when power is applied to it it whines in different frequencies as the LED flashes and then settles into a constant whine while the switch is ‘off’. If switched ‘on’ the whine disappears even if there isn’t a load. As my current requirements for plugs largely involve them being switched off 99% of the time in a quiet room and I also find the whine audible and distracting, I can’t really use it. I do have a replacement on the way though. If this is a one-off then fine but if it is a common issue I’d have a problem.
So my experience with them is limited to mostly standby very low power uses. I haven’t really found a reason not to buy them but equally only a particularly favourable deal has made them more attractive than others. Once you get up to about £28 a pop I think the TKB TZ68E comes in to play (Z-Wave without power monitoring) and the Hive Active Plug just about becomes an alternative.