Quick reality check. I just wanted to compare notes with someone who has tried this film.
I've shot a couple of rolls of Efke 100 35mm (souped in D-76 1:1) and I'm having a problem with the exposure. While other 35mm B&W films that I shoot seems to expose at their marked ISO, Efke 100 seems to want about a stop and a half more exposure to give any decent shadow detail. Also, when I process Efke 50 rollfilm, the presoak pours out dark from the dissolved antihalation backing while the 35mm comes out clear. There seems to be bigger difference in these films than just speed and size.