I have to agree with Colin as far as touch-screens and iPhone, although my 
comments apply to the Androids too.

The problem with a keyboard-only approach is it is not adaptable to various 
applications.  Yes, it works for entering text and numbers.

But, when it comes to all the other apps that have other functions, it 
becomes an incumberance.

I analogize it to the old Dos days.  Remember when every program had its own 
set of commands?  You exited Word Perfect with a different command than you 
did Word, or Lotus 1-2-3 or Como whatever.  All that kind of got more or 
less standardized with Windows.

At the time, many of us, including yours truly, went into Windows kicking 
and screaming.  I loved how Word Perfect was laid out, how I could easily 
tell how my document would appear in print.

Now that I'm a long-in-the-tooth Windows user, although I miss the usability 
of some of the Dos programs I was familiar with, there's no denying that it 
is a lot easier to become fluent in newer programs in Windows a lot more 
easily than you could in Dos.  This assumes, of course, that the program is 
amenable to some accessibility.

On its face, a touch screen will present some challenges to some people. 
For those who don't have a decent spatial sense and some muscle memory, it 
can be frustrating.  I certainly can't type as fast on my iPhone as I can 
with a full-sized keyboard; but neither could I type very fast with a 
condensed keyboard that one would have to use in a cell-phone sized device. 
What compensates for that if I have a longer missive to write is the Dictate 
feature available on the iPhone IOS 7 and above, or Siri or the Android 
equivalent.  There are also apps you can get that augment this if necessary.

Steve, K8SP