Allegro Stepper Driver IC

Can anyone report on their experience with the Allegro Microsystems SLA707x family of unipolar stepper motor ICs?

From the link above:

The SLA7070M series motor driver ICs feature unipolar drivers. The clock-in type input interface allows simplified control logic, and options for built-in sense current detection and load circuit short or open protection (patent pending) provide lower loss, and lower thermal resistance. All products in the SLA7070M series are pin-compatibile, supporting rapid design of application variants.

The built-in excitation distribution circuit (sequencer) allows motor control using only the CLOCK signal for simple operations (rotate/stop), with motor speed control by frequency input into CLOCK pin. This eliminates logic signal lines required for conventional phase-input methods, and reduces demand on heavily-used CPUs.