He created TetherGeist and has a few years experience with GameMaker. I give this 7-minute video an 8/10. He gives pros and cons. Great for 2D games, but not so much for 3D games.
not watched yet – 25 minutes, 1 of 7, made by GameMaker
@5:35 GameMaker gives the option of using GML Code or GML Visual. This tutorial creates a game in less than 15 minutes. It uses GML code. Simple, but effective. 8/10