The are many users of radiant water heat systems who are committed fans. You will hear talk of health benefits from less dry air and from not circulating germ filled winter air...
Radiant heating systems are simply those which rely on heating up an object which then radiates heat to the rest of the room. A wall hanging radiator that has hot water running through it is normal for such a system, but there are other ways of providing radiant heat.
Perhaps the oldest method known to man is radiant heat flooring - rich Romans in the days of Empire used it to keep those chilly mosaic floors nice and warm to their pampered feet. The water based system involves a boiler to lift the water temperature, a pump to send it around the home, and a series of pipes hidden beneath the floor. Many people really love this type of heating because the warm feet sensation makes you feel warmer in general - often the overall heating temperature can be lowered compared to other forms of heating. (They knew a thing or two those Romans.)
It is not only hot water radiant floor heat that is smartly out of sight. Hot water baseboard heat can also be very unobtrusive in the home, and also provides low level heat that rises pleasantly through the home.