Been playing online quite a bit recently. Some of the fps problems have gone away but there are no NZ servers which is annoying.
My KDR is at 1.46 or something around that at the moment. I normally play hardcore, but I don't care which mode. Whichever has free servers in Australia. Normally its TDM, CTF or DOM which are pretty fun.
I had one amazing match though where I was 27-1 at one stage with a 21 kill streak. I hardly knew the map either but was just on fire.
I normally use the starter rifle with a silencer. Can't remember the perks. Think I have sleight of hand, ghost, and ninja but not sure on that. On hardcore servers you don't need anything more than a 3 shot burst.