This article says that Metro trains were "mostly empty" during the first day of revenue service yesterday. For what it's worth, I drove past a southbound train that was approaching the Smithlands stop at Greenbriar and OST yesterday at about 4:30 PM, and it was sufficiently full that quite a few people were standing inside it. There were another six people at the stop, though they were probably waiting for the northbound train. We'll see how it goes from here. I'll have a pretty good view from where I work.