Counter-Strike: Condition Zero is the first official sequel to mod Counter-Strike, released in retail in 2004. It was pretty much same Counter-Strike on same engine and minimal changes when it comes to multiplayer experience, but it had more to often to solo players, with addition of bots and "Deleted Scenes" pack of single-player missions.
Now, for multiplayer community... Is as good as ever. While it's not on the level of Counter-Strike 1.6, you will still be able to find few almost-full servers, whetever it's yet another De_Dust2 map or some server that actually rotates maps. Just more smaller tighter community. BUT it's kinda way too high-skilled by now for newbies to be able to enter in easily.
So, when it comes to the main, expected, multiplayer part of the game, it didn't recieve many changes. Explosive grenades are stronger. Hostages are a bit more realistical. The end.
Oh, and you will ntoice that graphics got a small boost, as far as HL1 engine goes ("GldSrc"). Models got more detail to them. Few tweaks here and there. Maps are much interesting as far as graphical design goes. If you are going to play de_dust2 non-stop then better do it at the less bland one.
And yes, I don't really like Counter-Strike realistical gameplay much here either.
Now, for single-player, you finally get some bots to play with. Which are less frustating for new people than online play and helps to hone aiming skills as well better. Though, while they navigate through default maps quite nicely, they don't always make best decision. As a protip, always send them a voice command to stick together, team. They also try not to steal your fun of defusing bomb, waiting for commander to do it, even if said commander is in opposite end of map. Yes, it's a flaw.
And like Quake 3 Arena and UT, CZ single player consist of repeated matches with bots, as you will progress through trio of maps, being able to pick less and less stupid teammates over time, always being on side of Counter-Terrorists. And on each map, you have to have more than 2 wins over score of Terrorist team and have to complete each of three objectives, which go like "rescue <x> hostages", "kill <x> amount of Terrorists yourself", "finish some round in <x> time" and "kill <x> terrorists with <y> weapon". So, fun for a while, but more of "just so something was there".
And now for Deleted Scenes. This is what Counter-Strike: Condition Zero was supposed to be at some point, a full-blown single-player campaign. It was "cancelled" once Valve saw magazines giving it low ratings to preview, just to have it put along as bonus into final game. All just to get low ratings once again due to being "more of same". Deleted Scenes had 12 missions in retail release, with Steam version adding 6 more that you can select anytime from World Map.
Now, Deleted Scene is a mix of good and bad. The excellent level design and repetive core gameplay.
First, good things. Level design is quite good one. You will have to take control of unnamed heroes of counter-terrorist operations all over the world, with missions having great variety, with enough lenght to keep you playing, having to stop terrorists from taking over nuke in snowy part of Russia, defending yourself in Arabain town or fighting your way through the jungles. Seriously, some of the missions just have a bit of that scripted hollywood love that would make them worthy of being in Call of Duty and alikes, quite epic! Levels themselves are also build with knowledge of pacing and a bit of exploration, albeit linear.
And it really tries to push GldSrc engine! In order to make it look like it's capable of more than expected, developers made a lot of animations of death for terrorists as well as destruction animations. Hell, I was amazed to see a stack of boxes getting squeezed by a door in the third mission, it's all quite joy to look at even if it's scripted. And well, it does hurt occasionally when it comes to enemies deaths. Like, when you shot with pistol at melee enemy into knee and he suddenly teleported half-meter away to the door, swirled and fell toward the door, just to get it open.
But core gameplay of Counter-Strike doesn't translate well at all into linear levels of single-player. What you bassicly will do, is to shoot few bullets into heads, while taking some hitscan bullets back. Repeat it on every enemy. Until the end of the game. It really is repetive and boring. Weapons don't matter much, all of them are good enough for bursting enemy again and again. Grenades aren't given often and flashbang don't seem to be as useful as in multiplayer. Smoke grenade is more offensive there though, making enemies cough instead sometimes. There is little enemy variety as well, you just got whatever hitscan stupid enemy, stationary snipers with laser, whatever melee enemy that rushes you and terrorist with freaking bazooka that is pain to avoid too! So, burst headshot, and burst headshot, repeat repeat repeat.
It also finally get to have some music there. For once. So, something definitely good.
Counter-Strike Condition Zero is better offer than Counter-Strike 1.6 and has more value for solo players, but it's still not good enough to get me much interested in such twitchy realistical shooter. I still wouldn't recommend new people, especially with newer CS titles out there, only those who already play Counter-Strike should check out this one.