I hereby declare Lunar Flight to be my favorite Rift experience. It has by far been the best and most pleasant (read: least nauseating) experience. That might also have to do with me finally getting around to calibrating the correct IPD (inter pupillary distance) for my Rift.
Most likely the slow movement of the lunar lander and the static cockpit around the player is the main contributor in my case.
I really like that you can look around the cockpit as well - and when you look directly at a button you can activate it by pressin Y on the controller which is nice.
At first I tried to hook up the SpaceNavigator, which would be perfect for this, but it seems a bug in Unity only let's me register one axes (Z-) so until that's fixed I have to rely on the Logitech F710 gamepad.
However; it's not an easy game/simulator - so far no success, only crashes.
Now if I could only get to try out the famed Eve Valkyrie demo...