I pre ordered my rift and got it in the summer, and to be honest, it's getting better all the time. The picture quality has improved since release, due to various software tricks and updates. Agreed though that the definition is not as good as a normal 2D display. If you can imagine this, it's like being enclosed inside a spherical old fashioned CRT television that is all screen, 360deg in all directions around you, whilst wearing goggles and headphones. You can see the picture ok, but you are aware of the dot texture of the screen. The goggles limit the field of view if you keep your head still, but once you turn your head, there is 'infinite' fov.
I've tried Project Cars 1+2, Live for Speed, FSX+FlyInside, AeroflyFS2, WarThunder, and they are all excellent and I would recommend any one of them, but IMO DCS is the best one for immersion because you can feel what the flight model is doing so much better, so the Huey, Gazelle, P-51 and Spitfire are all amazing. I think it makes it easier to fly too because you have this peripheral sense of the 3D movement of the aircraft and you can stick your head out the window if you need to.
Also the sense of scale is striking, so landing the Huey on an aircraft carrier is great fun. Everything looks the right size like it never has in 2D. I can also recommend Manhattan in AeroflyFS2 for an amazing fR flying experience.