I have at least 6 Holgas, and 8 Dianas. They're so much fun to play with, and allow me to work looser. The reason I have so many is that (especially for the Dianas) there's such an inconsistency to them. Each one vignettes differently, the shutter works differently, and the f-stop works differently. They all have their own personality.
I've sold dozens of my Holga/Diana photos. I'm glad my buyers are more open to the images these cameras can produce than some of the people here.