Sonny Dickson:

We have managed to obtain several pieces of exclusive information that shed some light on what challenges Apple is currently facing with the project. According to our sources, the broad feeling of many working the project at Apple is that the device may be doomed to failure, and may not be viable at all unless significant advancements can be made.

The TL;DR version:

• Heat management issues
• Communication issues, both between the device and the pad, and the devices on the pad (for that really cool “Your iPhone tells you how charged everything is" function)
• Interference between devices

This certainly explains why AirPower was nowhere to be seen last week.