Mac Users: DO NOT upgrade to Oracle's Java 7. Doing so will prevent you from launching Spiral Knights.
If you are using Mac to play Spiral Knights, then the chances are that you are still running the old and outdated Java 6. But the rub is that the outdated Java will cause you to run the game at lower or choppy framerate with frequent lags which will become progressively worse with each update in the game.
Emailing the SK tech support team won't do you much good because they haven't been able to resolve the issue yet.
As far as I know, ALL of the Mac users in the Spiral Knights community are currently running Java 6. And they are all experiencing severe lag issues that grows progressively worse.
Ugh, I wish java 7 worked on Mac. Pretty much nothing uses it even though it exists, and everything requires using [crappy] Java 6. Such a pain in the [rump].