I once got an op-up from NRT-YVR (this was May of 2009). On this day- was a Monday- there was no flight #2 to YYZ, so flight 4 to YVR was oversold in Y. At boarding, I was handed a new boarding pass- seat 1A, which I took without any hesitation
I agree with the other poster about UA and UDU. I fly UA/CO/US a lot, and don't care for that policy, even though I often benefit from it on US. F (or really, J) on US is a joke. On a transcon you're experiencing the best they have to offer, and it is a mediocre meal, complimentary drinks, and a little bit extra wiggle room. Still sucks if the guy in front of you reclines. First class is really cheapened on these carriers, and IMHO they should just take a line from AC and call it "enhanced" economy.
I don't mind "paying" for my upgrades with eUpgrade currency or whatever. Now if I REALLY want a seat in J or F, I can also just pay for it
Outside of actually paying for a better seat up front, I don't think anyone is really entitled to one for nothing. As much as I like a complimentary upgrade, don't get me wrong, it is still a privilege and not a right, no matter how often I fly.