I'd like to share a recent experience:

On a full LX longhaul flight I wanted to check in with the e-checkin machine - it didn't work. I went to the counter and got my preassigned economy seat (23A). By chancer I chatted to somebody I know at the airport - she looked at my record and discovered something amazing:

During pre-flight editing I had been upgraded to C due to overbooking. I had been assigned 9A (business). I was checked in and right after that checked out again - both by the e-checkin machine. The upgrade got "kicked out"! Only by looking at my record history we were able to see that I originally had 9A. The ZRH transit counter then "onforced" the upgrade (last seat) after looking at the record history and finding out that a couple of TCGMs had been upgraded, and I as TCQG was still in economy.

Another tip: Don't try the machine for USA flights, it won't work and you won't get miles for trying.