The trend these days is to come up with devices that can do absolutely everything. Smartphones, for example, don´t just let you make phone calls, but you can send e-mail, plan your schedule, listen to music, watch videos, take pictures, record voice messages for later, surf the web and do all sorts of other tasks. Even simple mp3 players have turned into devices which can also play movies and games, keep your schedule and even wirelessly control your phone.
The theory of these devices is great — one small(ish) device in your pocket can do everything you need, freeing you from having to carry several devices to do everything you need to do. Reality isn´t quite so sweet and nice, though. Like a person who tries to do everything, the devices do a decent job of all tasks, but doesn´t do a really good job of any of them.
Say you are walking down the street and you see Britney Spears and you just have to have a picture of her (whether you want to keep it for yourself or sell it for a small fortune is your own issue). Your phone probably has a camera on it now, but your experience will tell you that the pictures just aren´t of very good quality. A good old fashioned digital camera will give you a picture of much better quality (though admittedly you can make a phone call on your camera). You have the convenience of having a camera with you, but you sacrifice quality for that convenience.
Now, taking candid snapshots of Britney have almost nothing to do with productivity. Other tasks do, though. Everywhere you look now you see someone sending or receiving e-mail via their Sidekick or BlackBerry. Both of those devices get rave reviews by users for their ease of use when it comes to sending messages to your colleagues. If you have had a phone conversation with someone using one of them, though, you know that they leave something to be desired as a phone. If you´ve used one to make a call with one you know that they have the styling and ergonomics of holding a brick to your ear.
Here´s the point — if you are trying to use a device that doesn´t do a job well to do a job you are probably costing yourself time. You wouldn´t try to shovel the snow from your sidewalk with a garden trowel, so why would it make sense to use an ineffective tool for portable productivity? If you are going to be using a mobile device a lot, do yourself a favor and get one which works as well as it possibly can.