German shepards great dogs. Extremely intelligent, very good with people and kids, and they make great watch dogs. Their size and looks alone can be a deterrent to most strangers, but for some reason kids don't seem to be scared. They can be extremely territorial, which is one of the reasons they make great watch dogs. You do have to be careful with them (or any dog), no matter how well trained or good natured they are, they are capable of doing a lot of damage very quickly. If you've ever seen any police dog videos, you can see just how agressive they can be. As with any dog, training is very important, if you don't train them early you'll have a really hard time getting them under control.
Females seem easier to train and shed less fur, and IMO look better, but I guess it also depends on the indiviual dogs. My current shepard happens to be an alpha bitch (vets description), which means she doesn't get along with other female dogs in her home turf. Outside the house though, she's fine with other dogs. I'm guessing its the territorial instinct. Hip dysplasia is a common problem also.