I received this email as well a week or 2 ago. As a LT Plat it really doesn't do much for me (but that is fine as I'm sure most MR members aren't LT Plats).

My issue is that it doesn't look like they ever gave me the night. When I add up the 15 nights from the CC plus my stays this year, that is the number of nights I see (no roll overs for me.)

I don't know if this is just an issue with my account, with my being an LT Plat, or more systemic to the system. So to those whom the extra night might mean something, you might want to make sure it was correctly added to your account.