Hopefully pulling no punches, I've been mulling over all the different form factors seen in the smartphone world in the last half dozen years. Is there a common consensus 'perfect' form factor? No. Could there be one in the future? Yes, I argue in The Quest for the Perfect Form Factor. And, to the point, at least one of 2009's smartphone contenders is achingly close, at least in terms of hardware, to the ideal. This being something of a contentious subject, your comments more than welcome of course!
"Over the years, personal and mobile computing has taken many, many forms, and, fifteen YEARS after Psion (with the Series 3) and Apple (with the Newton) started the whole thing off, we STILL haven't reached a point of agreement as to the 'perfect' form factor."