The T-Third is running in beta from now until April 1-- it's only running on weekends and every twenty minutes (though we waited about 45 minutes), but it's free if you get on the train at any of the new stations (from Fourth and King on down Third). Regular T service will start on April 1, at which point: 1) the N will terminate at Embarcadero and 2) the J will start running to the ballpark and the Caltrain station during rush hour.
We expect they'll be rehiring that lady whose voice does all the in-tunnel announcements to record her saying "T" -- as it stands now, the announcements go, "Inbound. N. In 2 minutes. ----. In 13 minutes." Once our train arrived, it was packed with people who'd gone to the Martin Luther King Jr. day celebrations, as well as a number of public transit enthusiasts. A bunch of MUNI employees were riding along as well, and they were probably the most excited of everyone.
We had a great time, and took some pictures, a few of which we've included after the jump. (And check out SF Metblogs' excellent coverage as well!)Picture of the fun advertising campaign for the T Third!