I took my 4.5 yo and 2 yo with their cousins last week. DD4 kept saying that she didn't want to go because she saw the previews with the witch. When her cousins said they were going, she couldn't resist an outing with her them. She ended up loving the movie. She tends to get scared of things easily, and won't even watch the stage show at the MK because Maleficent is in it.
I loved the movie, and was excited to see one of my favorite stage actresses in it. Idina Menzel who won the Tony for "Wicked" was Patrick Dempsy's girlfriend. I was just sad that she didn't get to sing.
I say try it. The worst that could happen is that you leave early.