Update 2: Ares I-X launch video:

Update 1: NASA has issued the following press release regarding the launch or Ares I-X

Today at 15:30 UTC, NASA launched Ares I-X from launch pad 39-B at Kennedy Space Center in Florida. Ares I-X is the first test flight of the Ares I launch system – part of NASA’s Constellation program to developer spacecraft and booster vehicles to replace the Space Shuttle and send astronauts back to the Moon and possibly to Mars.

The first launch attempt yesterday was scrubbed due to weather rule violations and, at one moment, a cargo ship which ventured into the splash down and debris fallout area. The weather today was not much better at first, with what seemed to be a never-ending violation of the triboelectrification rule, but about 15:20 UTC, NASA launch weather officer, Kathy Winters, declared the weather green for the launch attempt at 15:30.

Ares I-X ignition - Source: SpaceVidCast/NASA TV

Ares I-X liftoff - Source: SpaceVidCast/NASA TV

Prandtl-Glauert Singularity as Ares I-X reaches Mach 1 - Source: SpaceVidCast/NASA T

At about T+2 minutes and 04 seconds after the liftoff, the first stage have separated properly and continued coasting upward to an altitude of about 39.6 km before beginning its descent. The top part of the Ares 1-X rocket, called the upper stage and Orion crew module simulator, continued on an uncontrolled trajectory and crashed into the Atlantic Ocean.

Ares I-X First Stage Separation - Source: SpaceVidCast/NASA TV