Its a cheap and decent way to look at different panels of several types of planes and now it even has a couple that have G-1000 glass panels. On occaision I use it just to shoot an approach down to mins with really bad visibility to see if I can make it.
Now I wont say that it is a great "training aid/teaching tool" but it did come in handy for practicing some real world situations. After a 2 hour trip (real) had 1mi vis and 400ft ceilings. I shot a GPS approach down to mins - had to go missed - then flew to the alternate and shot an ILS down to mins (conditions dropped to 1/4mi vis and 200ft ceilings) - go missed - starting to get low on fuel and almost HAVE to land - shot the ILS again and finally made it.
NOW having said that I had practiced that same scenerio in a frasca simulator and the weather looked MUCH more real in MS Flight simulator X than in the frasca sim. Now of course the handling of the plane was much more real in the frasca sim, but FSX definitely had it beat on visuals.
There really isnt anything you cant practice on there, and you can set the weather to whatever you want. But just remember, nothing completely substitutes for the real thing.