[Imp]

If you play the game at all frequently you will kick yourself for not purchasing it earlier once you buy it.
You can play the game faster due to a combination of things, mainly better graphics & the formation ID letting you keep track of your units far easier.
Op filter makes setting up ambushes much simpler & more effective.
Extra features on the map editor are great if you ever make maps.
etc etc

Like many things the extras don't sound anything special ,put them all together though & you will be surprised how big an impact it has on your gaming experience.