They are really good for still life pix because they generally have excellent quality at high magnification, and large image circles, which grants you a lot of freedom of movement; important for table top pix. If you are using flash, no need to worry about not having a shutter. If not, you are best off with long exposures, so whatever you are covering the lens with (film box, lens cap, hat, etc.) does not show up in the pic. With my shutterless 5x7, I use ND filters outside to get speeds slow enough to get my film box out of the way without showing up.
I have used my 540mm f/11 Kodak Copying Ektanon for portraits and one still life pic on 5x7 film, and the pix look very good to me.