BlackBerry Curve 8520

I have used the Blackberry Curve 8520 for two years.

Pros : Good comfortable keypad. For those who are heavy SMS/Email users, it is a convenient phone to use - the keypad is much easier to use compared to the touchscreen keypads of Android phones, iPhone etc.

Using office applications like office email, office calendar etc on the 8520 is a breeze - the integration with Outlook is pretty seamless. If you work in sales, you can pretty much run your office out of your phone. (well...almost :)). The device also comes in built office suite - to open word docs, excel sheets and powerpoint slides - although documents with fancy layouts, animations, charts etc. often do not open properly. It sorely lacks a PDF viewer.

Battery backup is good - it beats most touchscreen phones in the market today.

Cons : You need a Blackberry internet plan to access internet on this phone. Such plans are often much more expensive compared to the normal 2G/3G mobile data plans. Also, you don't get the 3G data speed on Blackberry data plans - since this device lacks 3G. (I know ... for a smart phone to not have 3G is a cardinal sin).

Also the app ecosystem is really small - it has nowhere near the variety and quality of apps offered by Android or iOS app stores. Also, most apps don't work properly either.
Applications like Google Maps, Google Docs etc. don't work. Many apps that require an internet connection - like GTalk, LinkedIn etc. don't work over Wi-Fi - you need to use them only over a mobile data connection.
In short, it is a smartphone that can be quite ex[pensive to use - since the Blackberry data plans are all very costly.

Hope this helps.