We just returned from JW Marriott Ihilani yesterday and had a wonderful stay. We had a $289 MV rate with breakfast and were upgraded to a Deluxe OV room. We did not call, write, or anything in advance; just showed up and they upgraded us.

Now, one must keep in mind that your odds of getting upgraded on an award stay is much lower, even for Plats. IMO, paid Plat and Gold reservations will come first, and some hotels have a policy of not upgrading award stays at all - specifically the Vail Marriott Mountain Resort and Spa will not upgrade award stays. It is usually noted in the description when making the reservation as shown below:

"MARRIOTT REWARDS REDEMPTIONS*STANDARD RM ONLY*MX OCC 4 GUESTS*NOCONNECTING RMS*NO ROLLAWAYS ALLOWED*NO UPGRADES*SEE RATE RULES"