It's a skill based competitive shooter not for the faint of heart. I remember the first time I played and was tasked to take down a bunch of ruthless terrorists who were trying to destroy evidence of a weapons-cache in the shadows of Chernobyl, every night for the following week I had horrible nightmares of me being back on the battlefield watching my comrades die left and right .
I wouldn't really recommend CS:GO for the more casual gamer but aside from that you will encounter hackers and salty players like most games nobody can really say how often you'll encounter them but they're out there ready to ruin your parade.