Ah the gamification of phone purchasing... lets make the customer feel privileged to be even allowed to order one
But why not fulfill everyone on the waiting list in turn first?
If it works (and certainly appears to generate a lot of free publicity) then good luck to them I suppose - but it seems a bit of a tacky gimmick to me unless I am missing something.
If its like the oneplus 1 and doesn't support O2's 4G band, then its not much use for giffgaff! I'm not a fan of the snapdragon 810 either. I'm going to wait another year to upgrade.