Upgrades in my MVP experience are a crapshoot and not enough by themselves to justify keeping status. But if you like sitting in an exit row it's nice to be able to pick a seat when you book. You also don't have to pay for checking a bag and, if the gate agent allows MVPs to preboard (some don't) it's great to be able to store your carry-on reasonably near your seat and get buckled in before the really long line forms in the jetway.

And if you fly out of SEA the agents at the dedicated check-in station for MVP/F passengers are exceptionally nice people. I try to use web checkin but when I have a problem (seats are under airport control, etc.) these agents seem eager to help.