I'm so glad that I did mine. Not only did it give me a better insight on using the ADF and VOR's etc but you get to do holds and even ILS approaches.
This has helped considerably so far in two areas post IMC:
1. The ATPL exams (esp' Radio Nav and Instruments) you'll understand it better if you have an IMC.
2. The commercial involves 10 hrs of instrument flying, which you will be better prepared to cope with after an IMC.
Believe you me if you are slowed down on an already demanding course such as the CPL because you cant do an NDB approach or partial panel flying, you'll be kicking yourself for not having done the IMC.
Good luck with whatever way you decide to go!