How slow is the T?

It's so slow that Spatch actually saves 15 minutes by walking more than 2 miles home:

... Walking home from the Sullivan Square T stop not only saves me $1.25 per trip, but also around 15 minutes. That's right, it takes 15 minutes longer to catch an Orange Line train into the city and take a Red Line train out to Porter than it does to walk at a reasonable yet steady pace the two and a quarter miles from Sullivan Square to my place via Union Square. ...

Clicking on the link will also get you his account of street re-striping in Somerville.