From a Player Perspective
Want to see Combat Revision 2.0 changes from a player perspective? Check out Symmetric's An Introduction to Combat Revision 2.0 over at Radio MegaCity. (Adobe Acrobat Reader Reqired)

Keep reading below for a top-line view of the changes.

Removal of Zero-Sum Combat
With Combat Revision 2.0 in place, their is no longer one winner and one loser during each round of Interlock. Each round now results in either one hit and one miss, two hits, or two misses.

The only exception to this is when a special attack is launched during Interlock. If the special attack succeeds, it will trump the other player's attack, so only one player will take damage that round.

No More Tactic Number Versus Tactic Number
In the old combat system, two opponents' tactic numbers were compared to determine the winner in a combat round. Under Combat Revision 2.0, even a level-1 character has a chance to hit a level-50 character (and a level-50 can also miss a level-1). This is because each character's attack score is compared to the other character's defense score. This means you will get hit much more under CR2.0 than previously.

What you'll want to be more concerned about is your damage resistance scores. Each character has separate damage resistance scores for Ballistic, Melee, Viral, and Thrown (Stealth) damage. The higher your resistance, the less damage you'll take when you get hit. Damage is also mitigated by the level difference between opponents. A higher-level character will take less damage from a lower-level character. A lower-level character will take more damage from a higher-level character and may even take additional damage if the higher-level character significantly overcomes her damage resistance score.

"Always-on" Tactics
The four normal combat tactics (Speed, Power, Grab, and Block) are now always being used by characters while jacked in. Each provides specific bonuses to Ability attributes while on.

Because tatics are now used at all times, they have been moved to the Actions Panel and are available as hotkeys. If you begin a new character, these four tactics plus Withdraw will be automatically added to your hotbar for you. If you have an older character, make sure you add all five to your hotbar before engaging in combat.

By default, when you jack into the game you'll have the Speed tactic selected. You can change it immediately, and you'll continue to use that tactic until you teleport to the Loading Area or jack completely out of the game.

Melee Free-Attacks The old multi-on-one Interlock system has been replaced with the addition of Melee Free-Attacks. Players can now choose either ranged weapons or a melee-combat Style to attack with from outside of Interlock. Because of the addition of Melee Free-Attacks and tactics being available from the hotbar, the WASD keys no longer map to tactics during Interlock. (You wouldn't be able to move and use Melee Free-Attacks if tactics mapped to the WASD keys.) By default, new characters get tactics mapped to 1 through 5 on the first hotbar. You can move tactic hotkeys to whatever slots work best for you.

Combat UI Upgrade
The combat user-interface has been modified to improve use and feedback during and outside of combat. There are now two hotbars visible onscreen at all times and a total of twenty available rows can be accessed by either visible hotbar row. Hotkeys on the second visible hotbar can be accessed using Ctrl + # (the number of the hotkey slot).

When special attacks are activated from the hotbar, the slot number will flash red while the ability is queueing up for the next round. When the attack locks in for the next round, the slot number will remain solid red. If the special attack fails, a red flash will appear on the hotkey. If the special attack succeeds, a green flash will appear.

Each Interlock combatant has a green ring around his feet. If a combatant is going to take damage in the upcoming round, the ring will flash red.

Stat Influence Bonuses
Combat Revision 2.0 also makes your Stats (formerly "Attributes") more important in designing your character. Each Stat (Focus, Perception, Belief, Reason, and Vitality) now has a number of Influence bonuses that increase aspects of Abilities you use in the game. For every Stat point you have above 5, you get a +2% bonus to every Influence under that Stat.

Combat Styles
Each main branch of the Discipline tree now has an individual combat Style associated with it. (In the case of the Operative branch, there are many Styles.) Combat Styles define the strengths of your attacks, based on what is appropriate for that branch.

There are several ways to activate a particular combat Style. The most direct way is to activate it from the Action Panel or hotbar. Another way is to select the Style from your Close Combat or Free Attack dropdown. (Weapon Styles don't appear in the dropdowns, as the appropriate Style will be determined by the weapon you select.) Also, if you use an Ability that is associated with a particular Style, you'll automatically switch to that Style when you select the Ability.

All characters begin with the Self-Defense Style, which they gain from the Awakened Discipline.

Evade Shield Strength

Evade Shields no longer have a specific number of hits they can take before breaking. Instead, they have a number of points of "damage" they can withstand, which can be modified by the Evade Shield Strength Influence. If you have a bonus to that Influence, your Evade Shield has more "hit points". If you have a penalty to that Influence, your Evade Shield has fewer hit points.

This also means that your Force Combat Strength directly affects the number of points you take off an Evade Shield when attacking. Thus, a high Force Combat bonus results in a lower number of hits to break a Shield.

Withdraw Changes
There are a couple major changes to using Withdraw under CR2.0. The first is that Withdraw works just like other tactics--you select it and it continues to try to Withdraw you from combat until it succeeds or you change your tactic.

The second is that Withdrawing from combat is now a contested roll. Your Withdraw score goes against the appropriate accuracy score for the Style your opponent is using. If you win, you Withdraw.