I tend to agree with Joyride.
I have them setup as stand alone units without a monitor behind and I notice that clicking the buttons on screen with the mouse is usually just as convenient as pushing one of the buttons on the MFDs.
Also I agree with the remark about getting TrackIR steady.
It takes some tuning and is different with each game (I suspect due to FPS differences) but you should be able to get a fairly steady view with TrackIR. Try precision mode is one tip.
So while I think the MFDs are a cool setup to look at I dont feel them really neccessary.