HTC and Samsung are at the head of the line offering smartphones based on Microsoft's latest platform, which comes as a long overdue response to Apple's iPhone, Google's Android and the like. The new version features a tweaked user experience, focusing on touch functionality, with a renewed push to integrate business and personal tasks. Unfortunately, Windows Mobile 6.5 is largely considered a stopgap measure until version 7 arrives in the second half of next year -- so you shouldn't expect any groundbreaking new features.
The launch comes as some of Microsoft's high-profile partners, including Motorola and Palm, have moved on to focus their attention on Android and WebOS respectively. It remains to be seen if Microsoft's latest efforts in the mobile space can help it reinvigorate both market share and developer attention.