I didn't want to clutter up the discussion on wargaming and RPGs in general with more thoughts on Battlesystem specifically, so I thought I'd respond to that tangent seperately.

Basically the problems with Battlesystem were these.

1) The command, movement, and maneuver rules were basically cribbed from napoleonic and civil war rules sets (greatly abbreviated). This led to army formations, and orders of battle, and maneuvers that were completely out of place for a pseudo Medieval battle game. This perhaps is not an issue for many, but it was for me. The battle rules from Fantasy Wargaming were a far better historical period system in this regard.

2) The way monsters were handled were questionable. The idea of 75 Trolls marching into combat in a perfectly ordered phalanx just doesn't seem very likely to me.

3) D&D spells were on the wrong scale to have much impact on a battle field. Spells like magic missile, fireball, dig, walls that work well for skirmish size engagements are hardly worth trying on a battlefield...unless you have 50 level 5 magic users in a perfectly ordered phalanxe casting magic missile, fireball, dig and walls simotaneously....which the game not only allowed but encouraged...very very silly IMO.

4) Many implementations of special attacks / defenses and the like were implemented poorly or were down right broken. Take the above mentioned phalanx of trolls. According to the rules the unit could not move while it was regenerating damage. If it moved the injured troll was left behind and due to other rules regarding the integrity of formations essentially disappeared from the battle. Therefor Troll regeneration was useless. Dink the unit enough to wound 1 figure and the entire unit had to stop. If it didn't then no regeneration. Seeing that a small unit of elf archers could dink trolls like this all day, the trolls could never regenerate. Many of the rules were broken in this manner and required fixes

5) It was just heinously boring. There was no real feel of a force of Treants tearing into a force of Warg Riders. This isn't really surprising given that AD&D combat didn't feel any different whether you were playing Rogar the hulking barbarian or Lucious the daring bravo. It was just a very flavorless system. Any number of historical miniatures games could have been better adapted to fantasy.

Dink the unit enough to wound 1 figure and the entire unit had to stop

Yup. The rules were FULL of stuff like that. Mostly because many things were not explained completely in one section. For example the above troll rule required reading how regen worked. Then reading how units maneuvered. Then reading about whathappened when figures dropped out of the unit. Now I must add that most of them could probably have been handled by using simple judgment, BUT at that period my friends and I were in full Rules Layer regalia. EVERYONE at the table (including me the person who was doing the dinking to my friends trolls) knew it was dumb. But we spent over an hour in detailed rules citations and determined that that was in fact what the rules said.