I bought this phone to replace my BlackBerry and I am so happy with the features and usability. Other sites stated that this phone was tested for use on the ATT network. However, since the merger between Cingular and ATT I only could get a Cingular SIM card. To my surprise the phone worked great! I can easily use the GSM data network for email (set-up using the VOQ Mail Pro software) and I was cruising. The Windows Mobile 2003 software comes installed and ready for use. The interface and usability is much better than my 6120 monochrome Blackberry.
I picked my phone from Ebay for $119 (included shipping). Do not pay 4-5 hundred for this phone. It is discontinued from the manufacturer (which is really too bad). You can find this phone for 100-200 dollars.
I own a small business and will be buying these for my employees.