As they say the most fun you can have online in a shooter game. Ive so far clocked over 2000 hours into the game and even to this day I can hop into a match (unfortunately community servers only due to the current bot crisis that valve's official servers has) and still have a great time and even a few laughs due to the funny ragdoll physics and silly situations that can occur. Like just airblasting someone off a cliff as pyro and following them to their death as they stare you down.
9/10 would recommend to anyone, just stick to community servers.