Just picked me up a Samsung Jack, I love it. It’s responsive, it’s got the full tactile keyboard (touch screen wasn’t doing it for me), and it’s been flashed to Windows Mobile 6.1 from the Samsung Support Website (Simply search for “Windows Mobile 6.1” and you should find it).
The only drawback of the phone was how slow the “wheel” scrolls. This is configurable in the Registry. Simply browse to HKLM / Software / Samsung / KeyRun. Push the Values button, and look for WheelSpeed. Change the value to 0, and close the registry editor, no reboot required.
[Information Provided by MobileJaw.com]