Much more like Source, it's made on a newer version of the Source engine.
There are molotov grenades which create a fire blanket that slows players are little. It sounds crazy, but it actually played really well, I think, even though the size/dmg might need a bit tweaking. The other new nade is a decoy nade that can play firing sounds, so it can be used to fake that a player is in a position. Not sure how usable it is, but the idea is pretty nice, I think.

"It is a mix really, it has wall spamming which is more like 1.6, but it is on the source engine, so the feel of it is more (but not exactly) like source. The flashes are also more like 1.6, where turning your back to them will make you a lot less flashed than looking straight at them, but they also have the sound from source. The smokes are like they are in the current source. There is also more tagging than in source, but the tagging also depends on the damage you're being dealt, so you won't be pinned to the ground by being hit by a glock, for example

Features confirmed so far:
Planned release in Q1 2012
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)
Source

Features confirmed so far:
-defuse kits no longer purchasable. Now randomly assigned to two teammates at a round's beginning.
-new weapons including sawed-off shotgun, Molotov Cocktails and Zeus stun gun (humiliation weapon)
-Many of Aztec's changes have to do with the Terrorist spawn zone and additional cover near the double doors
-Valve still has a few surprises in store in terms of new maps and game modes.
-PC beta test planned for this October

I also noticed that Valve aren't being as sneaky/Secretive with this Project as they usually have done in the past.

Valve seems to be looking for heavy community involvement this time around (unlike CSS). A smart move considering the size and "temperament" of the fanbase.

I predict F2P, with hats.