I can run almost everything maxed up on a 2 year old machine (only turned down shadows and removed AA as I run it at full resolution). You do need a fairly powerful PC, but the game is less resource-intensive than ARMA2. Recently, the first chapter of a campaign has been released as a free DLC with very well done, really enjoyable game-play.
There are already quite a few of 'replacements' like the SA80 assault rifle and a full US/Russian weapons. The weapons and vehicles are all fictional (due to royalties restrictions), but they all feel real and there is a good balance between the factions' gear. Team-play, as always with ARMA series, is essential. Don't expect CoD stile game-play, but that's a good thing. Compared with ARMA2, the game-play is much more fluid, smoother, more FPS-like.
