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This is not uncommon in the graduate programs. So do not worry too much about changing the advisers / research directions. Students do not have to have such a "loyalty" to stay with the current professors for the entire graduate programs. Most professors would not mind your move if the both people's personalities do not match well or you are not interested in their research.

Keep in mind, though, do not bad mouth your previous professors. This will do no good to anybody and may hurt you as well. Otherwise, your new adviser would wonder if you may bad month him or her someday. Try to maintain good relationship with your previous adviser even you no longer work with him / her.

Changing advisors is no big deal. Many students do that in their course of their school years. Going through different advisors might allow you to expose to more insights and opportunities. There shouldn't be any hard feelings if you and your advisor do not work out as far as academic wise. Not everyone gets along with everyone or share similar goals that you envisioned for your future. At the end of the day, you are in charge of your own destiny and career. You definitely do not want to bad mouth anyone because it's a small world and one more friend is better than one more enemy.