Depending on when you fly, SoW and LDFM servers tend to be quite busy.
As Dietrich has pointed out above, SoW has had around 500 unique players join at some point during this month,
http://www.stormofwar.org/?Page=dcs/stats/overview
Over 1100 hour have been flown by humans since the start of May
http://www.stormofwar.org/?Page=dcs/stats/aircraft
Storm of War also has a very rich Ai environment, so even if there are no humans on, or few humans on, there is always air activity on-going such as bombing raids, recon flights, transport flights and AI fighter sweeps.