One advantage of doing the IMCR is that the proposed CBM IR will allow a credit for much of the IMCR training.
The current JAA IR does not allow credit for anything, short of another ICAO IR (e.g. the FAA IR).
Of course, all of this is in a state of flux anyway....
However my view, formed over the 12 years I've been kicking around this silly paper collection game, is that if you have a chance to collect a qualification, go for it. Especially one which is actually really useful. The IMCR will change the way you plan a flight and the way you execute the flight, very much for the better and safer.