I did it twice:

Last year on a very overbooked United flight to DEN: $300, a confirmable upgrade and a meal voucher.

And about 3 years ago on a London flight on United: $500 bucks, THREE UPgrades and four alcohol coupons.

I used two of the alcohol coupons in first row in coach (they stored my bags in the F-A closet becuase coach was packed) and went to sleep.

If you can do it, it's worth it. Nice move Dgolds.