Søren,
I have just started to develop my own E-6 with a roller and Jobo Expert drum that I will preheat to 38 C degrees. The film is outdated 8x10 Ektachrome and I believe my temperature control is not (yet) optimal as I only have a roller, but not the Jobo machine. After all, I am pretty happy with the first results that look more vivid on the light table than scanned http://personal.inet.fi/koti/cambo/index.html