The JAA IR is not for the faint-hearted.
Many folks I know (me included) decided it was more like academic study than practical piloting, and went off and did the FAA IR. That's vastly more achievable, but useable in IMC/IFR in Europe only if you have an "N" painted on the side of your aeroplane. That, too, is possible!
If you do the FAA IR, and use it a bit, you may be able to count most of the training you did for that towards a JAA IR - the rules aren't too clear (to me, anyway), but there is cross-credit.