All operations under general anaesthetic come at a risk. It is a tiny risk, but it is there. Not just for dogs, but for any animal and people as well.
Neutering a male dog is a really simple procedure that literally takes a few minutes. Minimal anaethesia is used. It is as safe as an operation can be.
I'm with with Kitty on this one though. I don't personally agree that every male dog needs to routinely be neutered. A lot of the benefits of castrating are for the owner, not the dog. If he isn't showing overt sexual behaviour, marking, aggression, or other hormone driven behaviours, don't feel you have to have him neutered, unless you are sure that is what you want.
Harley isn't neutered and is no trouble at all, even with an in-season bitch in the house. I will have him neutered at some point though, as he has a retained testicle. If both had descended normally I wouldn't bother.