Sadly the writing is on the wall for Bromma after BRA came out and said they could operate from ARN. I don’t see how BRA can survive then. They offer nothing unique and you might as well just fly SAS to Arlanda and at least get some points.
For some areas it’s actually quicker to get to Arlanda but Bromma has the added benefit of 10 minute check in times and very fast arrivals. It’s basically like a bus station. I flew to Brussels and arrived 20 minutes before departure and still had time to spare.