I used to teach the IMC a good few years ago, its a very useful rating to have.
I had a student who a few months after passing his IMC got 'caught out' in IMC with a fast moving front (he should have checked the WX properly, but thats another story!).
He got Luton to give him vectors for an ILS, they knew he couldn't except an IFR clearance in class A but but were happy to get him on the ground knowing he could fly an ILS they monitored like an SRA.
I think the rating gives the average PPL confidence on instruments and spatial awarenes. As already said, the sylabus for approaches segement of the IMC is very wide. Make sure your instructor at least does one of every tipe, ie. NDB/VOR/ILS/SRA/PAR.
NOTE : About 8 years ago the CAA would convert a FAA IR for an IMC. It will cost you less to go on holiday to the USA and complete an IR (40hrs less the 5 you instruments for the PPL and I think 10 can be 'mutual' hours with a friend under the hood, so 25 hours to pay for).
The US will except IR training into the major airports mixed in with the big guys, real good fun !