First and foremost, the Jehovah's Witness religion denies the Trinity. They also deny the deity of Christ, His physical resurrection, and salvation by grace. Another interesting and not-surprising fact is that they believe that they are the one and true church of Jesus Christ. With all of these facts, a person can conclude that the Jehovah's Witness religion is indeed a cult, not a Christian congregation. 
Adding onto NewLifeChristian their practice of disassociating members is awful. I know someone who was disassociated simply for dating outside of the church and now she cannot speak to her own family. They attempt to keep members ignorant and brainwashed into the "church" . Also, they don't celebrate birthdays, Christmas, or other "pagan" holidays. Jehovah's Witness and Scientology are both "religions" that are only "religions" because of America's very loose definition of a church.
Jehovah's do not make up their rules. They follow what the bible says. They follow what God wants. For example, is right to obey God for one day (Sunday) and then go back to being your normal self on the other days. It's not right. The trinity believes that there are three things making up god. God, Jesus, and the holy spirit but Deuteronomy 6: 4 says that Our god is one god. And why don't we believe that Jesus is god. If Jesus was god and he came to Earth, why did he pray. That makes no sense. And now Birthdays, there were only two birthdays in the bible and in both of them, someone got their head cut off. Christmas was not always the birth of Jesus, it used to be the birthday of the Sun God.