Tablet format is suited to a lot of things, but it’s really not suited to what we think of today as a “PC”.
What they are suited to is computationally intense display systems. Things like web-browsing, document reading, music and video playback, etc. Maybe tweeting.
But as a display gets larger, it becomes less and less useful to have an on-screen keyboard (unless you’re going to consider using haptic feedback to help touch-typists figure out where the keyboard is).
Start with the premise: This is not your personal computer, this is an interactive display. Focus on and develop those aspects, and then worry about adding a virtual keyboard to let me get fancy.
For example: A tablet is great for catching up on email, if you assume that I am going to mark out emails that need my attention to be dealt with later on from a PC, only writing replies with the tablet as a last resort.