Someone used the size of the USB ports to figure out the size of the whole thing:
Confirmed: Dell Mini Inspiron has a 8.9" or 9" screen
Will the Dell Mini Inspiron have a 8.9" screen, run Ubuntu or XP Home, and cost under $500?
That's what engadget seems to think.
We decided to do some measuring in photoshop to see if they are right about the screen size and here's what we came up with.

First we took a known distance: in this case the width of a type A female USB port (half an inch). We used that known distance to get the overall height of the ultra-portable: approx 6.6".

We then took a picture of the whole screen and transferred over our measuring rule adjusting it so that the measuring rule matched our known length.
From there it is easy to copy and rotate rules to find the horizontal and vertical dimensions of the screen: approx 5" x 7".
Who remembers their math classes?
"The sum of the areas of the two squares on the legs (a and

equals the area of the square on the hypotenuse ©"
In other words the diagonal length (aka screen size) of our screen is the square root of 5 squared plus 7 squared = sqrt (25 + 49) = sqrt(74) = 8.6"
A little of the screen is always hidden behind the bezel so we can be pretty sure the screen is 8.9 or 9": too big to be 7" and too small to be 10".
Does it come with Ubuntu and XP? well the keyboard has a windows key so we would assume that XP is an option (especially given Michael Dell's description of it being for "developing markets" to get around Microsoft's XP licensing requirements going forward). Dell isn't exactly renowned for supporting Linux but if their competitors are all offering Linux we can assume they will do as well.
Price under $500? Dell should be able to get cheaper unit pricing than MSI so an entry level mini inspiron should be possible for under $500 but we would hope to see a number of versions offered in the $450 - $900 price range depending on processor power, RAM, hard drive, operating system etc.