Introduction - If you have any usage issues, please Google them yourself
AccelStepper significantly improves on the standard Arduino Stepper library in several ways:
Supports acceleration and deceleration
Supports multiple simultaneous steppers, with independent concurrent stepping on each stepper
API functions never delay() or block
Supports 2, 3 and 4 wire steppers, plus 3 and 4 wire half steppers.
Supports alternate stepping functions to enable support of AFMotor (https://github.com/adafruit/Adafruit-Motor-Shield-library)
Supports stepper drivers such as the Sparkfun EasyDriver (based on 3967 driver chip)
Very slow speeds are supported
Extensive API
Subclass support