They are exceptional dogs, but require a dedicated and prepared owner, willing to commit more time and effort than you probably expect!
If you're really willing to put that in, I highly doubt you'll ever own another breed of dog ever again. My GSD is 3.5 now, and absolutely attached at the hip, far and away the most loyal dog I've ever seen. They are typically very high drive, high energy and very intelligent, which means they will demand your time and attention every day; exercise, training, discipline and mental stimulation.
Many, mine included are by nature wary of other people, and pretty indifferent to other dogs. Not aggressive, but she'll keep an eye on guests in the house, bark when a car pulls up, that kind of thing. She had a phase as a puppy where she was afraid of people she hadn't seen much before (kids, people in wheelchairs, cross country skiers, minorities, that kind of thing). That's where the discipline, training and your dog trusting you to take the lead are critical. She's over that now, but that kind of thing is really important to handle, and requires a lot of patience and work to accomplish.
If you do get a GSD, I'd echo what fatallah said, they can be prone to hip displasyia and a nervous system issue I can't recall the name of. Both, esp. the hips are more common in American lines (sloped back), and a good breeder will be able to show you history on either from the dog's parents so you can minimize health risks and/or be prepared.
Tl; DR. German shepherds are incredible dogs, and absolutely worth the effort, but are not a good choice if they don't fit your lifestyle or level of commitment to them. You need to be willing to commit lots of time, effort, training, patience and love. They will repay it many times over.