I'm not a regular fast-food-plus eater. If I want fast food I go for that and if I want mid-range I go for that. Steak and Shake is neither, it's in the middle somewhere.
Essentially what we have here is expensive fast food. Sure, the quality is a touch higher than the Big Three fast fooderies but perhaps not sufficiently so to warrant the extra cost. Then again, to each his own tastes.
If you're after a cheap burger, this ain't it. If you're after fine dining, this ain't that either. If what you'd like is a variety of burger options in a reasonably decent setting this they do nicely.
The shakes are rather tasty and the burgers are indeed a cut above the norm. If you don't mind paying more for what you get and aren't expecting a five-star out of burger joint then you'll be pleased.