We are playing almost every evening (around 21:00 CET) mostly 6v6 but also 5v5 or 4v4. There is no compatibility with campaigns or maps from original game. It's stand alone version, you dont need CD with game.
There is lot of new units of all kinds, new graphics, map objects (from ground textures to buildings), sounds, single and multiplayer maps. RWM is complete game modification with long history, it repairs some bad aspects of original game (primarily things like very limited visibility) and brings more realistic settings and unit parameters.