Im glad im not the only ex vet nurse who doesn't think that castration is written in stone.
I think dog temprements depend on several factors; breeding, training, environment, the "individual" dog. I do think an uncastrated dog will have a tendancy to be more dominant, but if this is a well trained dog, this should be in check and not become a problem. As i said, i have had two rotweillers - one castrated, one not - it was the one which was castrated that had "isshoos", but he was a rescue dog with a dodgy past so can't factor that in, apart from to say, a well trained dog shouldn't be a problem in this way.
Saying that, when i was young we had a lovely dog, who was uncastrated, probably fathered more illigitamate puppies than i cared to remember and was aggressive with other dogs in a big way. He was impossible to keep in, he was small lab size and would jump a 7 foot fence that my dad put up in an effort to keep him in. He would just make a run for it at every opportunity - randy little git.
So for me, im still undecided what to do with my JRT, but, he is begining to show signs of dog aggression, despite being well socialised, so if this develops i will have him "done".
It is interesting though - we are quite happy to castrate our dogs, maybe we should get our men "done" to deal with some of their testosterone fueled behaviour traints