I've been using the Metro and other mass transit systems in DC a lot this week, as in they're basically the only way I get around unless there's no easy path to where I'm going from the system. I've found it, every time I've been up here, to be reliable, generally clean, and inexpensive.
What I've found is that the shade some people throw on it seems to be very classist. That saddens me because I wish every city had this quality of mass transit.