Windows Mobile 6.1!!!

Top 5 reasons to update or buy a new smartphone with Windows Mobile 6.1:

1. Track your text messages. When you text with a friend, the messages are threaded together, just like instant messaging—no more confusion about what you're talking about. Discuss a project budget and view the conversation as you type, so you can refer back to important points

2. Set your style. Windows Mobile 6.1 runs on a growing variety of phones, including touch screen devices with slide-out keyboards, sleek full-keyboard smartphones, and compact flip phones.

3. Find it fast. The new Home screen design lets you put what’s important to you where it’s instantly available—on your phone’s Home screen. Place a clock conveniently on your Sliding Panel Home screen. Track appointments and messages at a glance. Get to your favorite songs, videos, and pictures with just a click.

4.Protect your data and your identity. Sync your smartphone with your laptop so if you lose your phone, you don’t lose your data. You can even encrypt personal information to help keep it from falling into the wrong hands.
5. Connect to Wi-Fi. Connecting to a Wi-Fi network is now simpler—no more scrolling through multiple pages. A single click to your screen and you’re connected.

Source: http://www.microsoft.com/windowsmobile/6-1/default.mspx