Wiktionary
early adopter
n. A person who begins using a product or service at or around the time it becomes available.
Wikipedia
Early adopter
An early adopter or lighthouse customer is an early customer of a given company, product, or technology; in politics, fashion, art, and other fields, this person would be referred to as a trendsetter. The term originates from Everett M. Rogers' Diffusion of Innovations (1962).