Are Males that bad?

Ok, Ive had bad times with male rats before. I had two and they just were horrible biters, since day one. I ended up being scared of them but I kept them none the less and let them live out there lives, but it made me sad. I also here about other male rats becoming nasty until the point where they have to be neutered.

[Im down for neutering, but maybe in the case of placing them with females and preventing mistake perggo's.]

If I ever got males again I would want to know, are all un-neutered males mean and nasty?
Have you ever had females and males, different cages, in the same room? Does it make the males mean or aggressive so they can get to the females or is it ok?
Should you just never get a male who isn't neutered?

If you have any more information about male rats I would like to know. I know they can be completely different then females and I mainly only have females. I would maybe get males later in time, no I would not breed, I don't want baby rats around. I just would like a lazy rat compared to my females who bounce bounce bounce! Thanks for the help.