My therapist is male, and he is fantastic. It did take me a long time to open up entirely, but I don't think that had anything to do with gender. It was mostly because I was not yet aware of what it was that I was hiding, and I was not yet ready to face them with anyone.
Unlike many of the girls here, I think I have an easier time talking to a male than I would with a female. I am not sure why, though.