"So you are now a new junior executive and your company tells you that you have to be accessible when away from the office. They tell you that you can choose any mobile phone that you want to, but you will have to consider that you will need to do email on it every once and a while. That pretty much knocks out the “free with your plan” phones and makes you consider a smartphone. Your only issue is that you have a PDA and do not want to have two devices that do the same thing. So now you have a problem: getting the smartphone and having everything on one device, with your PDA as your backup to everything; or get a high end phone that will be able to connect to your PDA (maybe even wirelessly), and you can have your email come down to the PDA."
BarginPDA.com has an interesting article that lists some pros and cons of the smartphone (small 's'). If you're thinking of getting a device, this article is a good source of the currently available devices by carrier, and the features / carrier packages that you should look into.