I flew on United from SFO to SEA on May 12 and they did board back to front, F last. The flight was probably 25% capacity so overhead bin space was not an issue. They told us to ignore the boarding zones on the boarding pass and wait until our row was called. On the same day I flew Alaska SEA to SFO and they were still using the standard boarding process. It hardly mattered since there were so few people that after first class, everyone pretty much boarded all at once.