Hi,
I've been diabetic for 33 years now and suffering from most of the complications, including ED. I blamed the wife at first (that "went down" well too!). My specialist had asked me regularly if I had been suffering from this but I had not. It sort of just happened overnight really. My GP started me on Viagra but, over the course of time the effect was less and less. Eventually he sent me to the urology dept where various options were offered to me. I'm now using Alprostadil (Caverject) injections. They work although the effect does seem to vary sometimes, between an hour or so and up to most of the day!!
I note that nobody has mentioned this form of treatment in the previous posts and it obviously is not going to be favoured by many, but it has made a huge difference for us (no pun intended) and it isn't as bad to administer as you might think...honest.