Experiences with Transcendental Meditation

Transcendental Meditation is a secretive mantra meditation movement founded by an indian yogi/guru. Most research on meditation benefits is on TM. To learn it, one has to pay for and participate in a course led by a certified TM teacher.

Does anybody here have had experience with TM, participated in a course and received a mantra chosen by their teacher?

Do you really need a teacher to learn it? Is the course worth it or just profiteering? Anything else one should know before going to a course themselves?