If you'd like a departure from the typical "harvest resources as fast as possible and build a huge army" RTS game mechanic, then COH will make you very very happy. Holding control points and strategically selecting what units to attack with and how to attack with them is key. A tank rush is nearly an instant fail. You must support your tanks with other units more suited to different tasks. The cover system is also an important characteristic. A lone machine gun in a field won't last very long, but build some sandbags around that machine gun and you have a very effective anti-infantry unit. The strategy is far too deep so summarize, everyone who's ever played an RTS needs to give this game a try.
