Decent burgers with a hell of a selection to choose from. Not great but better than most fast food joints.
They also have a great selection of shakes as well. The shake quality is just okay (I'm an ice cream snob so I can tell the difference). If you have kids then they don't give a crap and will love the shakes.
If you are looking for a high quality gourmet burger then go somewhere else. Steak and Shake is somewhere between a Wendy's and Red Robin.