For those guys who use "rings" regularly, do you really believe they "help" a lot? Have you ever had any issues or problems?

I am contemplating a couple as gifts for hubby, but still have reservations as the idea of constricting blood flow through those delicate vessels and the possibility of damaging that precious tissue concerns me. I would love to hear real world experiences from guys who do use these a lot? Am I justified in my concern or is it "all good" and nothing to worry about?

Serious advice and opinions welcomed.