I went from a traditional ANG position to an IMA position. It was a challenge for a number of reasons already mentioned above. IMA positions vary widely and your "mileage" will too. If someone would have asked me about it while I was in my first IMA position, I would have said no way. My current IMA gig is great and it's going to be tough to leave the flexibility if/when I go.
Bottom line, IMA can be great but, you have to do your homework on the front end. Find another IMA, ask them about the process. If you're interested in a particular position, find out what your active duty brethren expect of you.