Seattle got outsourced late last year, with some office/checkin staff moving to another airline, and one senior member of staff staying BA but relocated to MIA (he did know the ticketing system very well, and went above and beyond to get me out of a pickle just before they left).
It did go noticable downhill with the new outsourced staff, with one staff member letting me board the aircraft after the ticket scanner rejected my boarding pass as she didn't know what to do - it was because I was opup'ed as my seat was now taken, and then took the CSD 10 minutes of running around during the boarding process to sort it out.
I have been taking domestic legs out of SEA and joing the BA flight out of Chicago the last few months as the direct flight has been full, so I haven't seen if they have improved yet - in a few weeks when I come back I will.