According to the latest update, provided on January 15th to the Connecticut Siting Council, the Kleen Energy Power plant was estimated to be 93% completed. This was slightly ahead of their anticipated schedule, "It is currently estimated that the project will come on line in the summer of 2010..."
The project's transformers and switchyard building were complete, and operations of these were transferred to Connecticut Light and Power.
The picture on the right, and first one below are from the Kleen Energy report. The second picture below is from The Middletown Press, taken after the explosion.