I've had three CO VDB opportunities, all of which I have declined. In March and September, I was on SEA-EWR. They started with an offer of $400. In May, IAH-LAS, they offered $250.

While UA's VDB process was generally good to me last year (3x $400 and 1x $600 [I declined the hotel and cab voucher and it was the last p.s. JFK-LAX flight of the night oversold by order 20 pax]), I wish the GAs could be a tad more generous on occasion. Last Monday, I declined $400 for the last IAD-LGA flight as I was going to have to put myself on Amtrak to get in by the early morning and pay for my own cab (I stupidly forgot to ask about the US Shuttle out of DCA in the morning). Even had I declined the hotel, the agent wasn't willing/able to offer a cab voucher into the city. When I was still at the gate, they had exactly the right number of volunteers, so my guess is that someone had to get IDB'd as a result.