For those of you who signed up a year ago - my Prime was expiring on the 24th so I cancelled early, tonight, and was eligible for the discount immediately (it shows $99 when added to basket, but the discount kicks in once you start checkout.) I had to go thru CS chat to cancel because it was too late in the system to use the automated button, but they were very quick/helpful. The whole thing took less than 10 minutes, including both a cancellation & a confirmation/welcome email.
I am very happy this evening...