Took the trip last summer, and it was one of the highlights of our trip. Call ahead and reserve a window seat on the right side (I think, check the guidebooks). If they say you can not request it, call their bluff and threaten to call someone else. Being on the right side really makes the difference due to the standard path around the island. If you are planning on taking pictures (and the quality is important for you) get one of the aircraft designed for this. Our pictures were horrible.

I think, some of the people in the southern part of the island offer a trip where you can combine the copter ride with swimming and snorkeling (I think you jump off the helicopter into the water, but that sounds ridiculous to me now).

I don't know about the safety, I guess that would make me worry some. Our guide was a former navy pilot, so I felt fine with him.