I have been a member of Advantage Plus also for a number of years and can only agree with the others posting positive comments. Yes, the free night is subject to allocation as is the case with all "free" benefits - look at frequent flyer seats etc... People need to use common sense.

In all my dealings with Accor it is always stipulated that I must book this night in advance. I save my free night for either the Sofitel Sydney or the Novotel Manly.