Note that all of these features are from early alpha builds of the game and are subject to change or removal from the final release. See the sources list below for reference material used to compile this list.

Planned release in Q1 2012
Available on PC/Mac, Xbox 360 and Playstation 3
Matchmaking system
Focus on 5v5 competitive play
Both Defuse (de_) and Hostage (cs_) map types confirmed!
eSports-oriented
Competitive and Casual modes
Ranked / ladder play for individuals and teams
Dedicated servers
Gameplay has elements similar to both CS:S and CS 1.6
Classic maps (with both minor and major modifications) include: Dust2, Dust, Aztec, Inferno, Nuke, Train
Molotov grenade: creates area of fire that slows players crossing through it
Decoy grenade: emits fake weapon firing sounds to confuse enemies about your position
Bullets penetrate some walls and objects like CS 1.6
Many changes to weapons, as well as new weapons
Classic gameplay: no ironsights
Beta in September or October (Unconfirmed)