I only fly coach, and I'm rather extreme about it. Business and first have no value for me, so if I get an upgrade, I feel someone else should really get it because they seem to value it and I don't for sure. I try to turn them down, and I mostly succeed. I started a thread "the down side of upgrades" several years ago, and people thought I was joking, but I wasn't.
And yes, I'm flying to Asia next month.