Issue of free will is interesting and linger from the foundation of Judaism and predates Christianity. It was again debated by early Catholic fathers and later by St. Thomas. Modern fundamentalists like JWs diverge from doctrines and debates of Jews, St. Augustine, and Thomas by understanding what free will is. Jews believe that free will allows us to violate the Torah. Catholic church believes that our free will is limited in our capabilities, but we have free will to choose to sin. Another interesting point Judaism teaches, that angels do not have inclination to sin, but they may if they are materialized on Earth. Pretty much the humans can have a bad influence on spiritual beings. Angels who destroyed Sodom were banished on Earth for 133 years according to Judaism because they did not tell the people of city that they are condemned by G-d but by the angles themselves. Satan in Judaism is not someone who rebelled against G-d, but he is hired by Him as a servant and public accuser. There is no anti-polar view of bad Angel in Judaism as opposition to G-d.
Notion of free will is complex that I get lost in reading in St. Thomas' Summa Theologica:
http://www.ccel.org/ccel/aquinas/summa/FP/FP083.html#FPQ83OUTP1