I've had a Drayton Wiser system installed for a while now (maybe 3 years) though it is a VERY simple setup. Did it all myself.
It replaced an older Drayton Tempus 7 system which in turn replaced a mechanical clock system built in to our gas boiler.
Very simple to do, though IIRC I did need a new mounting plate as the older Drayton version was subtly incompatible on physical mounting, the wiring was exactly the same.
We only have one (wireless) thermostat, usually now in the lounge, replacing a wired Honeywell wall thermostat in the hall. Much better location.
So it controls/schedules hot water (old-school gas boiler with gravity/convection circuit) and central heating (pumped of course).
There is a thermostat on the hot water tank but that's been there for ages and the Wiser isn't aware of it, it's effectively part of the boiler hot water controls.
No radiator thermostats or any other extras.
The manual says very clearly it's NOT suitable for such old "gravity" systems, that's hogwash. I even asked Wiser directly and got the same answer.
The Tempus 7 system had a jumper that you set to ensure the water was always switched on when the heating came on, the Wiser has no such option.
So I just programmed it to ensure that the central heating time periods were always within a hot water time period.
In fact I've subsequently found than when you override "out of hours" and turn on the heating the boiler fires up anyway, even though according to the manual it shouldn't. So that's fine.
Things I like:
Remote access when away.
Mobile/wireless room thermostat.
Easy programming via App on iPhone/iPad.
Things I don't like:
Dependency on the manufacturer to keep running their internet service and your registration account.
Only App access, no web browser interface.
All the clever extras in the software, they seem to be rather too clever in many cases, certainly for us. And I'm a retired IT guy, man and boy!