Arma2 is an amazing game but still has some really bad design too. For example a lot of the stuff you need to learn, is only really tought by doing the campaign, and the campaign is awful :/ Harvest Red in particular. At first I thought it was just an ugly, clunky, boring FPS. It was only once I got to about the fourth mission and started flying around the huge country in my own chopper that I realised what it was all about. And even after finishing the whole campaign, there's still a lot to learn when it came to playing online.
I think the best way to learn stuff is by reading the forum and watching youtube movies. Hopefully Arma3 will ease players in to the game better.