all depends on the origin/destination/day/time.

eg:

-Today, mid-morning MSP-EWR E-170: There was an open F seat and all 5 of us who were flying in F were upgraded. So any premier flyer in that flight was upgraded
-Monday, early morning ORD-MSP A319: There were 59 names on the upgrade wait list in addition to the ones who did get upgraded.