Old game, new engine, boring outcome.
The graphical engine is obviously the Source engine that is also to be found in games as Half Life 2, SiN Episodes and more which renders really nice looking enviroments and highly detailed textures and effects but it's not enough to stand alone as a new game - said before, this game is after all just the same game that's been on the market for about a 7 years already.
You'll play in teams, either in the Terrorist team which in most maps has the goal to set up a bomb in either of two alternative bomb-locations and once placed, defend it from the Counter-Terrorists who have the goal to either kill all the terrorists or defuse the bomb once placed. And there's also some maps that plays out as a hostage-rescue situation where the Terrorists have taken hostages and it's the Counter-Terrorists job to get them out of there to the evac-position but in the same time defend themselves and the hostages from beeing killed. Everything is happening over and over again but what's making it a little more fresh is the fact you will be able to gain money from how succesful you were during the last round and from there buy new weapons from pistols, machineguns to grenades and other gear to help you out in the fight. The arsenal is also different between the different teams, the Counter-Terrorists are using the standard US and British weapons such as the M4A1 Carbine, FAMAS and M249 S.A.W. while the terrorists will be able to buy weapons often shown in middle-eastern areas as the AK47 as the well-known example. Both teams will be given acces to the same pistols with little difference, grenades and flashbangs and other gear such as Night-Vision Googles and Kevlar.
The weapon models are really high-detailed but isn't that true to their true design and functions at all times. And the tactical element in the game is something you'll rarely found while just playing on official servers - it's mostly about just running and gunning and using some glitches to found your way to superioty. And you'll find these little kids everywhere violating the language with all these trendy Internet-"words" and finding many, many generelly nerdy people around the communities which is always as frustrating and annoying to play with.
Despite the nice graphical engine and many of the new, really good sounds the game doesn't stand up to be a new game - and is only to be recommended to the fans of previous installations in the series.