In my view, IMC Rating students should be told up front that if they want to really use all the privileges, they will need a decent aircraft and do perhaps 20-30hrs/year as an absolute minimum. It will also take more than 15hrs training. So there is a minimum cost which well exceeds the cost of the test. But probably nobody will tell you this; they want your money!
Otherwise, the IMCR is still very useful for those cases where the vis is bad (you can fly on top) or where the forecast is a bit ambiguous as regards visibility etc. The extra navigation skills (VOR/DME) are absolutely worth having, aren't at all hard, and in my view every PPL should do them!
It's a pity though, because e.g. the ILS is such a potential lifesaver. It would be a great shame to lose that skill. I spoke to an RAF pilot the other day; they are taught the ILS in their basic training. If I was training one of my children for a PPL, I would make sure they can do an ILS.