Polyelectrolyte solutions exhibit unusual or unexpected properties in the limit of low salt concentrations. Consequently, theoretical treatment and interpretation of results obtained by various experimental techniques meet many difficulties. Application of photon correlation spectroscopy to this problem is discussed on the basis of numerous results obtained in a wide variety of experimental conditions (charge density on chains, concentration, molecular weight, temperature, dielectric permittivity of solvent). Linear flexible macromolecules, poly(methacrylic acid) and sodium polystyrene sulfonate were used as samples. The multicomponent character of the solution, i.e., the interaction between charged macromolecules and counterions, is shown to be very important. Experimental results are compared with existing (rather controversial) theoretical concepts.