Some information:
DCS is THE combat simulator. It is a free platform where you can add payware addons. It comes with a Sukhoi 25 and a P-51 two seater.
In terms of flight simulation maybe is the best, but only for a reduced amount of planes and choppers.
Menu is not as friendly user as Microsoft simulators or even X-plane.
It is not global, I mean the scenery is only a part of Georgia.
Updates are automatic when you start the sim.
http://www.digitalcombatsimulator.com/en/