Unlike others who have posted, I have had one fitted for quite a while now, and have certainly found it useful over the winter months. I’ve never had a problem with the signal wherever we’ve been (and that includes many out of the way CL/CS’s) - perhaps I’ve just been lucky?
We’ve used it either when we’re away, turning the heating down or off when we’ve gone out, and then turned it up/on an hour or so before we’ve gone back, or whilst not being used (we’re lucky in that we keep the caravan at home and on hook-up) to keep the inside above freezing for obvious reasons (despite taking all precautions and using a Floe unit etc., etc.).
So, personally I like it, but accept that it won’t be for everyone. Only you can decide really whether it’s worth the outlay.