It's a drag and drop game editor with very basic scripting elements for the "Advanced users". I use it time to time to do some prototyping on concepts but that is about it. I also wouldn't call game maker a Game Engine, because in reality it is a drag and drop game maker.
You can produce some decent quality games but it will give you no where near the control you have when coding it.
So basically you won't be doing much coding in it(If any at all) but it can produce some nice little games and can be helpful for prototyping game ideas or certain features to see if they would be fun or not.