Retention was biggest thing I was surprised about in gamedev. We've had massive dropoffs from level to level with something like 1% of players making it 3 quests in - with 1 player finishing them all. I guess it isn't too shocking when I think about the status of my own steam library.
You have any analytics in your game or you've just been looking at the steamworks stats?
RE: Player retention seems to have gone up a bit since the latest Revulsion Patch.