They had an attempt Saturday which aborted at T-0.5s when one of the nine engines had excess high pressure. The software caught and safed it. They traced the issues to a balky check valve, which was replaced on site and the rocket recycled for launch in a few days.
Last night was the second opportunity and I'm glad I stayed up to watch because SpaceX successfully launched!
The Falcon9 had a smooth countdown and on-time liftoff. After staging, the Dragon's Merlin vaccuum engine fired up and boosted it the rest of the way to orbit. That separated and the solar panels deployed (the Dragon has wings!), which was a new milestone for their hardware in this mission. It seemed like a perfect launch.
Over the next few days, they'll be testing the maneuverability and control systems of the Dragon on orbit. Then they'll pass around the ISS and, if approved by NASA, move to close approach. The astronauts on the ISS will use the robotic arm to catch the Dragon capsule and mate it to the station's docking collar. (I assume that Dragon will be designed to handle this autonomously in future.)
Also, just confirmed is that Dragon carried Scotty's ashes into space, per James Doohan's dying wishes.
Congrats SpaceX on the launch! Let's hope the rest of the flight proceeds as smoothly.