As others above have said, it is NOT the easy option. I did the FAA IR in Florida earlier this year, and the standards are way higher than the IMC rating. How they compare with the JAA IR I don't know (not having the spare sack of gold to pay for all the extra training that requires). The FAA IR is certainly based on practical piloting skills and situational awareness.
The oral is about as tough as any exam you will ever do, and the flying requires you to demonstrate *everything* in the Practical Test Standards. Even the JAA IR doesn't do that.
If you have an N-reg aircraft, it gives you the same privileges as a JAA IR in a G-reg. And you don't read of US commercial aircraft getting into difficulties because the FAA IR is so "easy", do you!