I just checked in for GVA-AMS-DUS tomorrow without any problems. For the first segment of this trip, I was assigned a middle seat in the middle of the cabin (around row 9 as far as I remember). I have no problem with a middle seat from time to time, but it was easy enough to change it to a window seat further back (row 21). I really don't understand why the system allocates middle seats to elites, when that obviously would what they least wish for.
I only did OLCI because I have an early-ish start tomorrow, and I am going to risk the CFF (Swiss train company) not planting me in the middle of nowhere on the way to the airport (will arrive 08h07, flight leaves at 09h10). Otherwise, for the 20 or so flights I have done during the last month, I have reverted to airport check-in because that has always yielded a better seat.