Check out
www.ontrackaviation.com for the requirements and content of the CRI(ME) course, or you could look at LASORS (but you knew that didn't you Mr Instructor?!
)
You need 500TT and 30 PIC on multis before you start, which means most don't get to doing it for a while. I would say it's worth it if you know you can find work instructing on a multi or if you want to move toward commercial instruction.
Personally, I'm working on getting the supervisory 'R' removed from my rating first before I do other things - have you got rid of yours yet?