Do you call it a convertible tablet or a convertible ultrabook? ASUS is calling the Transformer Book a detachable notebook.
The ASUS Transformer Book is a Windows 8 convertible tablet/notebook that's powered with an Intel Core i7 processor. This means that it's much faster than any of the Atom-based processors, but it also consumes more battery power as well. So, that's the trade-off that you must consider. The Transformer Book also has a larger 13.3" screen which means that the overall device is going to be larger and heavier compared to many other Windows 8 tablets. Battery power on this device is 38Whr (Pad), 23Whr (Keyboard Dock).
The ASUS Transformer Book is also one of the few detachable tablet/laptop combinations that includes a backlit keyboard. I'm sure more future models from all the other major manufacturers will include backlit keyboards as fairly standard features. Right now, the 2011-2014 time period seems to be when we're making the major transition to follow after the Apple MacBook Air and include backlit keyboards on even ultralight and ultraslim PCs.
One of the major reasons why my HP Folio 13 ultrabook is still my main laptop is because it has a backlit keyboard. Once you've experienced it, you can't live without it. If I could remove the screen on my Folio 13 and carry that around like a tablet, that sure would be nice.
Here's a short video that describes the ASUS Transformer Book: