I've used some of the older roll film backs, specifically those made by Graphic and Calumet. This biggest nag I had with every one of them was they were prone to light leaks. Maybe it was just a function of there age. I was able to finagle the Calumet to where it didn't leak too often. All depended on when/how the darkslide was pulled.
As far as work flow goes, there's the extra steps of having to remove/reinstall the ground glass-for this reason and the way it attaches, a Grafloc back is mandatory. Someone in a forum said the Calumet was designed to be inserted like a film holder with the ground glass still on - darn near busted the GG trying to do that.
The other thing is one has to be very fastiduous in advancing the back to the next frame immediately after exposure. There was no interlock to prevent double exposing.
As far as focusing goes, there's no change. Use the GG or on the Graphic, the range finder.
Aside from all that, they ain't bad. If you want to shoot MF rolls and have the advantages of a view camera, a roll film back will work. I haven't used mine though since I went to 8x10. Why I'm still hanging on to it I don't know.