Scott wrote

As I mentioned elsewhere, I am experimenting with LED lighting.

Me too.

I was having a curry with a former colleague last
night, who mentioned his father hates LED lighting

Just another dinosaur IMO.

for the following reasons:

These are all bogus, just a rationalisation for being a dinosaur.

1. The spectrum is too narrow thus depriving
the body of the right kind of light.

Plenty of other stuff is MUCH worse in that regard.

And the same silly claim was made about fluoros too.

There is no 'right kind of light' that the body must have.

2. HIgh frequency flicker, higher than fluorescents

Just as true of CFLs.

possibly triggering migraine.

Not a shred of rigorous scientific evidence of that.

3. Because of the frequency (colour temperature?)
the light does not travel as far

Nothing to do with frequency or colour temperature,
this is due to the physical detail of the light source.

so streetlamps need to be placed closer together
but. Councils are not doing this for cost reasons,
leaving blackspots in illumination.

Irrelevant to what is viable in a house.

In fact it's the opposite with a house, because led
strips are possible with leds and not viable with
other light sources, you can get much more even
and shadow free illumination in places like kitchens
and with work surfaces. And its much easier to have
the most suitable colour temperature too and you
can in fact have completely programmable colour
temperature that can be set by the user for only
a little more than a fixed colour temperature.

Is there any merit in these arguments?

Nope.