A few weeks ago, I went to work without my Macbook’s power adapter. To make matters worse, I used my macbook on the 1.5 hour commute - Net result, I only had a 2 hours battery life for a 9 hour day.
Luckily for me - I had my iPhone (Lucky is incorrect, I always carry it). I had never considered my iPhone to be as business capable as previously owned Windows Mobile & Nokia phones, but it disproved that in a hurry.
I did have my email configured on the phone so that was not a worry. What really helped me out that day was Quickoffice, an app I had installed on my phone for over 2 months, but never had an opportunity to use.
I moved all the relevant files (2 documents and a ppt) I needed for the day, to the phone, crossed my fingers and watched my Macbook save memory state and shut off.
As far as email goes, I had no issues. The iPhone had been quite impressive handling emails since I started using it. What I did need to do was configure quickOffice to edit my attachments. This was a circuitous route that involved sending the attachment to a specific email address and then re-downloading it in Quickoffice.
I realized that day that the biggest problem with the iPhone is that apps cannot access the file system. A very misguided sense of security.
Anyway, Quickoffice does allow quite usable editing tools, considering it is a mobile application, allowing me to finish 2 documents, and read up another couple from mail.
At the end of the day I had to charge my iPhone in the middle of the day the iPhone helped me retain my productivity (granted it had been a slower than average day :p).
It is obviously becoming apparent that devices like iPhones, Windows Mobile sets, and other smart(er)phones have the ability to take over from a computer for day to day tasks.
The next step should be a universal docking station, where any smartphone can be plugged in, and provide a keyboard and a large screen monitor I am looking forward to it.