Just as I as I wrote some time ago here UMPC cannot replace my laptop yet, Shaun from Palm247 echoes my concern about viability of all-in-one device in his article The all-in-one PDA will never happen
"... In reality, the physical restraints of a phone make long periods of office work almost impossible because the keyboard is too small or the screen is unable to display enough information at any one time. Many of us look at new devices and probably think “This is the one!” This could be the device that will enable me to actually work away from the office, but it never is. There are always new smartphones hitting the market that claim to let you “take your office with you” and they are not exactly lying. It is true that you can edit documents on a smartphone and that you can send and receive email, but just as I would not want to play snooker on a 2 foot x 1 foot table, I do not really want to do lots of work on my phone..."