Formal and simple, it is not your usual RTS, rather a tatics game.
This is Rock-paper-scissors taken to a sort of extreme. For example, there are various categories of vehicles, which are countered by various weapons. Tanks are vulnerable to rockets, and not so to lasers, while hovercraft are vulnerable to flak weapons, but not so to ballistic weapons, and so on.
There are some issues: Even with compatibility mode on Windows 7 it still has graphical issues, and the difficulty increases rapidly on the slider, becoming very difficult unless the slider is far left (though with this argument Age of Empires II is also unfairly difficult as villagers seem to be produced at an alarming rate.)
Overall a refreshingly different and formal game which is intelligent and well thought out.