-very little lag sometimes
-your gameplay experience will vary based on your skill level (learning curve is very high if you're not familiar with fps, i.e. PEOPLE WILL RAPE YOU IF YOU'RE NOT ALREADY GOOD, but there are some noob servers)
-Classes are well balanced, there's always at least one class that will fit your playing style (example: shitty aim? pyro)
-yes, dedicated servers as well as player hosted
-There is ALWAYS plenty of servers with open slots
THERE