I think an IMC is well worth it
1. You've got to build hours so you may as well do it constructivley
2. It does wonders for your flying
3. It allows you to hour build even when the weather isn't great
4. You can practice IMC/R.NAV during hour building ready for CPL/IR
5. It helps with the ATPL's
6. Holding an IMC can count towards certain amount of your IR training
7. It can get you out of sticky situations.
Mine cost me £1500 in the UK, I have seen them advertised for £1300. Not bad for 16.5 hrs training.
As for the minima on appraoches, my understanding is the minima for an IMC rated pilot is the higher of; the proceedure value and the pilots licence priviliges (plus any personal minima).