I'm not convinced that a sim forum is required - AVSim et al have it well covered. Having said that, there is a natural commonality of interest. It was flightsim that made me realise that flying can be accessible to anyone, not just airline pilots or the military. If it hadn't been for flightsim, I wouldn't be bankrupting myself in my quest for a PPL right now. Yeah, cheers Microsoft!
I learnt a lot from simming - I felt comfortable in a plane straight away. Anything that reduces the learning curve a little has to be a good thing. I have had to swear off flightsim for a bit though - I don't want to develop too many bad habits...