I'm also considering how best to prepare for the IMC rating, and have considered whether to try instrument flying on FSX before starting lessons.
One of the criticisms of flight sims for VFR flying is that they can get you into bad habits that it's then difficult to break out of. I wondered whether there are any similar concerns regarding FSX for IMC flying.
e.g. would I be better to take a few real-life lessons to develop my instrument scan before trying to work out how to use the nav-aids in flight sim..?