Never had a Holga, but at Ohio Univ we had to use a Diana F to set everyone equal in the 101 to 115 level photos courses. The light leaks alone drove me crazy. My dad had a 6x6 Rolli and a filter retaining ring for it and he let me take it to OU for 3 terms. I picked up a glass cutter from a hardware store and would pick up odd pieces of glass and cut filters for the TLR. Had some amazing images from all kinds of glass. Would hand them in on my class Diana F assignments but would never show anyone my contact sheets because there were no light leaks from the TLR camera and they would probably boot me out as a photo major for trying to be inventive.
I have seen many people using the Holgas now and I have to wonder about getting into glass collecting again for my future Diana F / Holga wantabees images. I think I just talked myself into this.