The hardware details are largely obscured, but what is obvious is that there is a definite home button -- much like the one on the iPhone. Additionally, there seems to be a cut-out in the casing which could reveal a front-facing camera. Using some image editor trickery, Engadget has also determined the screen size to be as expected, roughly 10 inches.
These images seem plausible to me mainly for the fact that they reveal very little information. Also, the fact that the hardware details are hidden from the photographer seems very Apple-esque. If I remember correctly, Apple did something similar during the development of the iPod.
Over in the Twitterverse, notable Apple watcher (and TUAW founder) Jason Calacanis is claiming to have had in his possession a pre-release Apple Tablet; he had some back-and-forth with Matt Schlicht of Ustream, who also intimated that he got an early Apple present. Some of the hardware details that have been "leaked" are a front- and rear-facing camera, 10-inch OLED display, HDTV tuner, and a low-power mode specifically for reading ebooks.
The information about the multiple cameras and low-power mode are definitely plausible; however, the use of an OLED display and inclusion of an HDTV tuner would indicate some sort of funny business. Given that Apple is in the business of selling HD television shows, it seems weird that they would make it easy to get that same content for free.
One thing we know for sure, though, is that with less than four hours until the start of Apple's event showcasing its latest creation, things are really heating up.