Reserves are neatly handled in the game. Units in tactical reserve will move to support a friendly unit being attacked in an adjacent location. Local reserves will move to support a friendly unit being attacked anywhere in a location within their remaining movement point allowance. Moving and attacking are as simple as point and click. Pretty neat touch.
Movement has a couple complications.
Enemy air units assigned interdiction missions can make sudden attacks. Your units will tire and lose effectiveness. A big downside is that units which have been split up and later recombine will take a proficiency loss regardless of casualties. The game factors interlocking ZOCs, unit facings, terrain and weather into it all, too. I think it has to do with changing the time frame of a turn in a scenario and getting numbers that didn't jive, even when the time frame was shifted just a little.