SpaceX stopped this morning's "demonstration" launch at T -0.5 seconds. Pressure was too high in one of the engines and they're not gamblers; they shut it down and they'll try again on the 22nd or 23rd.
Despite headlines (CNN has blurbed it as a "fizzle") this is pretty impressive; I don't think a Shuttle launch could be safely aborted with a half-second to go, not with solid-fuel boosters already lit. SpaceX, on the other hand, is going over the hardware and telemetry and will have another go once they find and fix the issue, possibly as early as 22 or 23 May. They're in the freight business, not the stunt business.
This is a real launch with a real cargo, destination ISS -- but it's all nonessentials. It will be the first run-through of the docking procedure.
STANCOR 10P TRANSMITTER: UPDATE 12
5 days ago