Many different sources of input are available to assistive technology innovators during the course of designing products. However, there is little information on which ones may be most effective or how they may be efficiently utilized within the design process. The aim of this project was to compare how three types of input--from simulation tools, professional therapists, and end users--affect the final design when they are provided during the course of the design process. Eight design teams were recruited to independently design a working prototype of an assistive device while receiving a particular type of input. Twenty potential users were recruited to evaluate each of the devices with respect to effectiveness and satisfaction. The results indicate that in some cases each type of input can have a positive effect on end user evaluation. Issues related to how input may be affected by design concept selection, stakeholder recruitment, and timely delivery of input are discussed. (Contains 9 figures and 1 table.)