It depends on how you want to progress your career, and where you are in your ATPL studies.
If you have the ATPL theory under your belt already, I would go straight for the IR, and then the CPL later.
If, OTOH, you are over a year away from doing the next step / rating, I would definitely do it. It is a very useful rating to have, and also gets you back into some training halfway through hour building, which should really sharpen your flying.