when I trusted the AI to do a reasonable job, the game game really cam alive to me. I used to control everything at a Bn level, plus ART, and i did horrible my first few times playing. Plus it just makes larger (300+ units) games and long games (3+ days) unmanageable, IMHO. Now, when I can, I probably use REG attacks 80% of the time. And watching the AI combine some Panthers and some Mech Grenadiers for an assault on a tough objective is a thing of beauty. You really have to pay attention tot he commands you give it though. 90% of the time, when I notice a Bn or Reg doing something wonky, its because of the orders I gave it (ie, "quickest" vs "covered").
You can also "lose control" of units when you issue orders in a rapid fire way. The orders delay just doesn't keep up; which I think is a great feature. Also, tucked in all the features is the actual stats (force date) that will tell you how competent the unit is. And if they're fatigued, they just don't go anywhere and won't respond to your orders. I've been burnt by that. Anyway, I'm sure you know all this already.