This combo unit is a temporary fix designed to address the fact that you can't get all the computing power to run Windoze effectively in a thin tablet.
If you could get all the functionality in the tablet alone, you'd just add a case that includes a bluetooth keyboard to your pad. That's what iPad has done, but the iPad doesn't have the power to have this solution meet power-computing needs.
Over time, the screen will be the largest component and all the computing power will add very little to the size of the hardware needed for the screen. It's happening in phones, tablets and PCs.
A convertible or hybrid seems more restrictive than just buying a bluetooth keyboard if you need one.
The more I buy gadgets, the more I include the case and accessories in my purchase decisions. For example, the Touchstone in the car is a great addition to the Pre. The uniformity of iPhone/iPad guarantees many accessories designed to work with it. I also would never have a pad or netbook without a case, so I consider the functionality added by the case in my decisions.