We’ve found the flic buttons to be very reliable, moreso than some of the zigbee buttons. We have ours paired to a tablet which serves as our home automation center, so it’s always plugged in. There’s one tablet on each side of the house, which works well for us. Ours are definitely more reliable for us than the Fibaro zwave button, which we had to return.
Different things will work for different people. I don’t expect to see Flic change protocols any time soon, as they have a larger market opportunity with bluetooth. For example, Flic buttons now work with Wink.
It would definitely be nice to see some more zigbee buttons with this kind of rubbery material! Of course, it would also be nice if SmartThings turned on the hub’s bluetooth radio. 
As mentioned above, you can look at the buttons/small remotes that do work with zwave/zigbee at the Buttons FAQ link. Choice is good. 