Is the Oculus Rift 3d only?

Sure you can. That doesn't mean you can just set up the display in the Rift as a second monitor and play your game on it though. Your left eye would only see one half of the screen and your right eye the other half. Instead, you'd need the same image to be shown on both sides of the display. This would have the effect of having a screen in front of you that fills your vision.

Well actually, it will not work as a normal 2D monitor. This is because it uses a single screen and splits it between the eyes. So normal 2D content will look very strange and will not be nice to look at. In addition, even duplicating the same 2D image and showing in both eyes won't work either, since there is partial overlap between the eyes.

In short, only specifically coded applications and games will be supported by the Rift.

The Deskope program from AngelJ will let you view anything on your Windows desktop inside the Rift. The desktop appears as if projected onto a large curved wrap-around screen, and the Rift head tracker lets you look around at different portions of the desktop. Newer versions of Deskope also let you resize the desktop, to minimize neck strain.
:D

@cybereality

doesnt fit here but i just noticed: ur Avatar is amazing, its how i imagine the rift to be in its perfect form ^^ please tell the devs to make it like that :D (geekmasters is good too ^^)