Some servers give you a good ping but then have bad server lag after you start playing. In game lag is well hidden and so your left with a bad, frustrating experience.
If you get on a good server, the game is a blast. The AI bots are also hit or miss depending on the server. You can run into ultra deadly bots or brain dead simpletons that don't like to fire their gun.
Weapon choice, weapon addons and the body size you choose are a key thing. Progressing up to level 20 doesn't take long.