It patches a number of things, but mainly squashes the disappearing party member bug. You can read the notes here.
The notes hint that patch 0.7 is just down the road and includes subscriber content. It's worth noting that the Guy Fawkes event ended nearly two weeks ago and that subscribers have essentially been playing the same game that non-subscribers play. I don't know if this is the big December patch everyone is talking about or something to whet the appetite before it.
We shall see.