We're told to expect an oleophobic Gorilla Glass screen with a standard XGA (1024 x 768) resolution, options for 16GB, 32GB or 64GB of storage, optional WWAN, an accelerometer, gyroscope, light sensor, microphone and a battery that'll last for around eight hours in ideal circumstances.
Combine these offline capabilities with device APIs that allow web apps to access hardware features like cameras, battery level, microphone, etc and Mozilla could effectively break down the barriers not only between HTML5 and native apps, but between high-end mobile devices and low.