I can only speak from the stand point of RC Helis. It has been my experience that the sim is very similar if not harder than the real thing. I learned everything that I know thus far from the simulator. I have translated that into real life with no "major" crashes and very valuable experience. In my opinion and from what I have read that of others also, the simulator will not be a waste of money. I know it hasn't been for me.
At least look at it this way, if it is raining boot up the sim and you're still flying. Seriously though, it's worth it.