I haven't played in a while, but it's not bad for a free FPS. But at the same time the more popular it gets, the more they're going to lag. But at the same time it's reasonable, attachments are nice, and the backpack is nice. Oh, the K2 is awesome as long as you're not worried about repetitive stress injuries.
Oh, and some people I know from the tubes set this up because Nexon's official forums are held together with tin cans and string and are largely unmoderated: http://www.combatarms.us/