I believe I have played with everyone on the roster at least once other than Nate, Ender, and yourself. Not actually sure about Ender. I've spectated, but not necessarily played?
There is a good deal of familiarity between most groups of people you could extract from the playerlist. I've played with a number of people here more times than I could count (e.g., Mac, Dizzy, Marmot, Wilgy, etc)