I've edited this announcement so it's a little more current.
The servers are mostly stable now and running fairly well for most players. There is still occasional downtime and we continue to optimize / improve / and fix problems as they come up, but in most cases they should be running fairly well.
In order to update the servers we sometimes do have to restart them. So if you lose connection just try a little while later. Most of our restarts are pretty quick. (<10 mins) Also look for broadcasts in game or announcements on the forums for scheduled downtime.