Just about every muscle of your body will get trained with this movement.
The main thing to remember with pin pulls is to try and get in the same body position you would be in with a regular dead lift at the same angle. Too many times lifters step too far off the bar when they should be right up on it.
Also, do not make this a leg pressing lift. Keep your head up and PULL the bar with you upperback and glutes. Think of this as a hinge with your body. It's a deadlift, just with a slightly shortened range of motion.
This is max effort at its best.