I usually do not have flexible plans, so I rarely take advantage of bumps. However, this summer on vacation to Scandinavia, SAS asked if I were willing to be give up my coach seat SEA-CPH in exchange for a guaranteed business class seat the next day, along with a free hotel night and a $600 voucher for a future flight on SAS.
I took the bump, but then SAS could not locate a hotel room within 2 hours drive of SEA, so I drove home in a rental car at my own expense. After a lot of hassle the next day, I was reimbursed for the rental car, received my seat in business class and flew on to Copenhagen. After a lengthy search for my luggage at the airport (it had traveled on my original flight and had been "secured"), I exchanged my $600 voucher for $300 cash, as I really wasn't interested in future SAS flights after all the hotel, luggage & rental car runaround.
I had a wonderful vacation in Denmark and Norway, and then traveled home on LH through FRA, with no further difficulties. But I wouldn't be likely to take another bump - not worth the hassle.