Last week I tried to use the machines at LHR. It told me my ticket was not valid. The ticket had been misprinted (Routepass issued 20MAY, expires 21MAY), so I wasn't surprised.
Anyway, yesterday I tried again with a new Routepass ticket. I already have next year's BD gold under my belt, so I am now back collecting on LH M&M. I put in the ticket and my Luftymiles(tm) card, and the machine offered me my flight, then a seat. I would have preferred a window, but it said there weren't any available, so I chose 20C instead. It duly printed my ticket, but without a seat number. As if by magic, a Helpful Person appeared. When he checked on the system, he said I had been put on standby (this was despite having a confirmed reservation), but managed to find me a window seat. He then found I had two seats booked - one with my DC number, and one with the LH number. He eventually managed to delete the spare booking and, three boarding passes later, put my miles onto my LH account. He also gave me an upgrade, which was nice.
In short, I was not too impressed with the machines, and won't be rushing to use them again.