Peter, I happen to agree with j3. Not that this should be the sole tool for maintaining IFR proficiency - but I frequently use X-Plane to practice approach procedures - and in my opinion it's a far, far better platform than the synthetic trainer at work, which CASA has seen fit to certify as approved equipment to maintain approach recency.
MS Flight Sim, X-Plane etc. are great when used properly, as procedure trainers. Nobody's suggesting they replace flying an aircraft - but none of the approved synthetic trainers do either.
I hammered all the approaches I was likely to get in my MECIR flight test, the week preceding the test, on X-Plane - and it helped immensely. The procedural side of flying under the IFR was very comfortable to me from all that practice - so all I had to worry about was actually flying the real thing accurately in IMC.