I've been bumped several times using e-tickets or tickets in the self service machine, and then just asking at the gate as this is where most (all?!) bumping decisions are made. Just make sure to go there early and to offer your help if they are overbooked...

Regarding upgrades, I have no experience possibly due to the reason that I always use the self service machines... My guess would be that it's more likely to occur if you are checking in using an agent rather than using a self service machine... Remember that you can go to the checkin agents with e-tickets as well. They simply swipe your card instead of the ticket.
There have been occurrences when the the self service machine has been unavailable for check-in "for this flight", and I have had to check in with an agent. When checking in I was told that the flight was oversold (they didn't need any volunteers though...).