Seems a reasonable enough question to ask as it's just a tool to help one's film shooting.
I use my Lumix GF1 as I would have used a Polaroid back. It's great at 100 ISO but relatively noisy at 400 and above. I presume later models have better noise control. However, the 20mm lens mine came with gives me very similar coverage to my Rolleiflex and Mamiya 6. Most importantly, it also has the option to shoot square as well as 2:3 and 3:4. When shooting portraits on 120, I find it very useful for testing and showing the sitter.
And a hot shoe too.