The IMC rating in itself is a good initial exposure to the basic theory of IR flying. Using it in anger to go from A to B with your PPL, observing your own sensible weather limits, is worth its weight in gold when it comes to hour building. The confidence you gain makes the practical side of the IR training easier on the brain than having the minimum IF training alone.
Should you envisage a considerable gap between achieving an IMC rating and training for an IR, can use the rating practically and can afford it, I highly recommend it.