Much more like Source, it's made on a newer version of the Source engine.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