Currently, the Seattle Metro Bus Tunnel is only open on weekdays from 5 a.m. to 7 p.m. These hours mean that I rarely use the tunnel. Most of my non-work bus riding is on the weekends or night after 7 p.m.

The good news is that once the tunnel starts having the light rail go to-and-from the airport, the tunnel will be open on the weekends!

I sent feedback and got this response from Sound Transit:

When Link light rail starts operating, the tunnel will be open on weekends. Passengers will be able to travel from downtown Seattle direct to the Airport.

This is awesome. I hope that busses will also use the tunnel on the weekends — it makes for a much more consistent and less confusing transit system (which is always a Good Thing in my book!).

UPDATE 10.08.07
It looks like whether the busses run in the tunnel on the weekends is still up in the air:

The 2009 rail operations plan calls for the tunnel to be open weekends and also late at night during the week. KCM bus operations will have to decide if they wish to run but we at Sound Transit plan to run the train week ends and to continue to use the tunnel.