I subscribe to widewing's, plus I would add some accuracy to field Ack, especially short range shots. Besides it's weird behaviour (you more likely be dead if you make a very fast pass than a slow one), there is, IMHO, a general feeling of safety when you reach for the field, either in a Buff or in the regular suicide porker Jabo.
If that Cloclo AAR about attacking a field is trustworthy of what Real Life ack was, AH is way too tender to enemies.