They are quite useful in terms of abstraction (i.e., the “For” in Fortran), e.g.:
a = 'there are '//.str. 400//' items'
print*, .hex. ptr
print*, 'hello' .in. strings_set
vres = .nabla. p - v * dt
The unary ones are nicer, since they have the highest precedence so no parentheses are required.
And IIRC even the IMSL libraries defined a bunch of them (.x., .xt., .tx. and so on).