I use a Singer Graflex 6x7 holder on my Toyo View. My darkroom isn't set up to enlarge 4x5 so it allows me the versatility of camera movements on a format that I can handle.
My experience is identical to Alex's and he covers all the points that I would make. I never noticed any light leaks when I used it in the studio but the first time I took it out in bright sunlight I noticed a problem. Now that I am aware, I just drape my darkcloth over the back of the camera while the slide is out (I swear that I will work out a more elegant solution... someday).