The IR aspect is pretty good - you can practice all sorts of instrument maneuvers in any conditions you specify - fog/night/snow/cross-winds/vacuum-failure etc. You can also do it in busy traffic, although communicating with ATC isn't particularly good - all we need now for that is good voice recognition (shouldn't be too hard for a flight sim - the language is fairly well locked down - not like a full English conversation after all
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And if you get it wrong it doesn't hurt your insurance
Just thought - with new MS FS-X, there will be people taking the role of ATC. I imagin there will be a community of people extablishing themselves to help people 'train' with proper voice-comms. I stumbled accross a web site a while ago where they teach people how to fly the helicopters in FS2004 using their own training location add-on, voice comms, etc. I don't see why the situation won't improve with FS-X.