They are almost useless for serious heating setting though.
Not if you know what you are doing.
I like to think that I know what I am doing in relation to basic matters and I must disagree.
The problem comes because people think they will measure the temperature of pipes as required for balancing. The angle of view will not cover a 15 mm tube and the tube is round and not flat either.
Then there is the emissivity of the surface. If everything was painted matt black then they would not be too bad but on white or shiny copper they are both inaccurate and misleading if anyone believed the reading.
They can be used for comparative readings if its realised that are not showing the real temperature. For balancing use on the rad flat surface at the inlet and outlet rather than the pipes as DIYers expect to.
The contact thermometer is the only way to get correct accurate readings!
I actually do this kind of practical work whereas we gather that D Hailsham is a retired armchair expert who may not even own an IR thermometer.