Perhaps I missed the announcement and the discussion on flyertalk, but I noticed this today on the
elite levels and benefits page MVP section:
Effective for tickets purchased after February 28, 2012: Unlimited** Complimentary Upgrades anytime on qualifying fares (Value Fares booked in S, or B, or Full Flex fares booked in Y), or 48 hours prior to departure on other fares. Qualifying Mileage Plan number must be in the reservation.
Interesting, so they added restrictions to the MVPG guest upgrade certificates to eliminate discount fare upgrades, and then add instant upgrades on Value fares for MVP's. So...the end result is an attempt to sell more higher (instant upgrade) coach fares...