I got involved with an evangelical group in college and they would do 3 day retreats. Here's what I experienced:
1) I loved the music & funny skits they would do.
2) I loved the warm feeling, bonding, togetherness, time to think about things, etc.
3) Here's the dark side though: they wanted to see me get "born again" or "saved" or "accept Jesus as my personal savior," etc. They are hoping you will believe as they do and will pressure you to give yourself over to it - to just let go and surrender yourself to the "holy spirit," etc. They will give you attention, talk one-on-one, use persuasive reasoning, Bible verses, and emotional appeals.
4) I gave into the pressure & became one of them. 15 years later, I regret that decision, am angry with myself for succumbing and am angry with them for creating a potent mix of pleasure and pressure to accept something one might not otherwise accept if the love-bombing and music, etc. weren't there as Aussie Oz rightly called a "hook." Some people, including myself, can be hooked by it.
Still, it sounds like you are curious, and I am a risk-taker myself, so I won't tell you not to go, but it's worth being aware that they might try to mess with your head & heart.