My favorite features in ACE are the simple stuff, that just makes the games so much more realistic and immersive. Some examples:
Realistic AT-weapons:
- Disposable AT-weapons where applicable, no "taking 4 law rockets" kind of "cheating"
- AT-weapons have ballistics, so the rockets won't just fly in a straight line forever. Takes some skill to use effectively
- Wire guided and laser guided weapons work like they should, no magic autolock for Metis for example. Also applies for helicopter weapons
- Larger variety of AT-weapons on the opfor side too
- The required skill makes specialists more important and the role fun to play. Especially good for squads.
Weapons and gear:
- All the M16 and M4 class weapons come with IR lasers, flashlights and CQB sights as well, like the MK 16/17 class in OA
- Ability to use IR laser and flashlight on the same weapon
- Loads of new weapons with a more complete selection of attachments
- Different grenade throw animations for more control, especially in CQB situations
- Flashbangs and CS gas
- Fragments for grenades
- Ability to flip the GL sights up and down on some weapons so you can actually see your iron sights while not firing grenades (very important
)
- Weight limits for gear: can't run forever with 50kg of gear on your back. Makes specific roles in a team more important; one man can't be a machine gunner and demolitions/AT-specialist at the same time. Also makes assistant roles more important, not to mention transport vehicles.
- Have to carry magazines for crew served weapons; no magic magazines hidden inside the gun
- Backpacks for all units
Specialist roles:
- Specialist roles are important and more fun to play. AT, Demo, MG, Sniper and other roles take more skill to play and you always feel like an important part of a team. This is especially good for squads with specific roles
- Employing armored vehicles or air vehicles take more skill and it's a lot more rewarding to play them. Everyone can still fly but it takes some knowledge and skill to choose the right weapons for the right job and use them effectively
Other features:
- Increased survivability in vehicles; You can no longer kill a helicopter pilot by shooting him trough the windshield with an AR. You can't disable an armored vehicle by shooting it's tire our with AR caliber weapons. Helicopter tail rotors won't break from a few AR rounds, and neither will the main rotors and engines get disabled so easily
- No magic radars for tanks and armored vehicles
- Ability to change weapon loadouts for air vehicles
Obviously there are a lot more features in the mod but these are in my opinion some of the most important. Most of these features are features that in my opinion should have been in A2 in the first place.
Even though there are a ton of features in ACE, you don't really have to worry about learning them all. If you just want to be an infantry grunt, (and let's face it, you will be infantry 99% of the time in CiA sessions) you don't have to worry about most of the advanced features in the game at any point. Most of the features are very simple and logical, much like you would expect them to be if you hadn't gotten used to the somewhat dumbed down gameplay in vanilla Arma.