Our system has a smart thermostat that quite successfully anticipates heating requirement. The best way to use such systems is to minimize the temperature differences between night and day to no more than 2 Centigrades.
That's not really practical with our radiant heat system, as we have 12 thermostats... and maybe I missed one or two while counting. Each bedroom has one, each full bathroom has one, two in our main hallway, etc. There are also three central A/C systems, each with its own thermostat. For these I am considering replacing them with internet-connected ones which can have remote sensors, but I just haven't got around to it in several years. I'm getting lazy in my old age.
Apparently this is cheaper/more energy efficient than turning the system off at night and starting up again in the morning. They say this is even more true with a heat pump as source. Anyway, now that we have improved the insulation of our home, even early in the morning on a freezing day the room temperature is still quite comfortable. So we have reprogrammed the clock on the thermostat to raise the temperature even later. By that time the sun has come out in force (we have huge windows facing South East), even in winter, and the heating system no longer comes on until the evening. Insulation is the key, for energy conservation, but also for comfort.
In our case we have floor heating, but also a few small radiators, and they respond much faster. If you bury the heat lines deep into the concrete the system will obviously be much slower than when you have them closer to the top.
The radiant heat systems here for slabs are actually rather sophisticated. Not just tubes in concrete. Multiple layers including insulation and vapor barriers. You also have to be careful with carpeting, like choosing a thin, dense, rubber padding (which costs a lot more than foam padding), and dense low-pile carpeting. Stone floors can develop cracks if the water temperature goes above about 120F. Wood flooring is not recommended at all. Ceramic tile is the best for in-slab radiant heat, though tiles have their own pros and cons. We didn't design our house, and knowing what I know now I'd probably still go with radiant heat, but I would use ceramic tile throughout the house. I've never been a fan of wall-to-wall carpet, which is so popular in the US.
I should also mention that our boiler is gas-fired. I've talked to a couple of people in our area with large solar arrays and they've installed electric boilers, and both went to tankless hot water heaters at the same time. They both had nothing good to say about tankless hot water heaters (reliability issues), but they thought electric radiant heat boilers were better than gas if you have a solar array of sufficient capacity. The gas models do not have variable output burners, but the electric models do (element modulation), which makes them more efficient. Without solar electric radiant boilers are apparently very expensive to operate, so they were told.