*shrug* Sounds like a pretty normal day for United Express.

I'm flying them tonight...last flight out of Denver (although possibly a different actual operator than your IAD-EWR flight). I always check hotel availability and know what my backup plan will be if they cancel.

I've had multiple UX flights in my life where I've rerouted myself to Hertz.

Not the most reliable bunch, and mainline UA really could care less how UX treats you. At least you got bit on a short flight where a rental car or a train is a feasible option.

For whatever reason (perhaps pure luck), my US Express and American Eagle experiences have been more fortunate.