Finally...
We sold our car.
We've been thinking about doing it for about a year. D has been using TriMet almost exclusively since she started attending graduate school, but I drove to work at my previous job and for the first year of my current one. Last April, after learning too much I decided I was going to start taking the bus as often as I could. Since then, we've driven our car only two or three times per month, and with that transition complete, it was only a short jump to getting rid of the car altogether.
Now, we'll save on insurance, maintenance, gas, etc. And using TriMet and other services when we need them will be vastly cheaper, to say nothing of the other benefits.
When we need a car we can always use ZipCar or even rent one, but one of the great things about Portland is that if you live relatively close in, you just don't need a car. The key is realizing that.
Not having a car is really liberating. Woohoo!