The 3D glasses don't apparently cause any problems looking at screens that aren't running in 3D mode, because each eye sees the same picture on it regardless of when the glasses switch eyes. All you get is a dimming effect where the displays don't look as bright as they should - kind of like wearing sunglasses.

From what I've heard, FSX works quite nicely with the nVidia 3D kit, but certain graphical elements, particularly point light sources, appear at the wrong depth and look rather odd.

My projector will do 100Hz, not 120Hz, but I gather you can fudge it so the nVidia drivers will work because 100Hz is double the standard PAL frame rate. I may splash out on the glasses and see how it looks.