I'm having issues with online play, will take an age to find a game and then I will randomly lose connection, I never had this issue in the UK with a download speed a quarter of what I have now.
Although I am not sure if the issue is HK or Black Ops related, a lot of people in the UK and US are reporting issues as well, although they seem to be talking about lag which I don;t really have an issue with once the game is loaded.
What is really bugging me is not being able to hear footsteps, guys have literally run up right behind me on a wooden floor and I have not heard them, this includes people who do not have a high enough rating to have purchased Ninja.
I was never a soundwhore on MW2 but it's nice to know if someone is about to stab you in the back...