With the new version 1.5 you can assign your primary MobileMe calendar to sync with the default calendar in Microsoft Outlook. Any other MobileMe calendars you have will continue to sync with Outlook and appear as separate calendars. The new control panel also delivers improvements for syncing bookmarks between Internet Explorer and Safari, and provides compatibility with Windows 7.
If you are already using the MobileMe Control Panel, you can simply upgrade to iTunes 9. This will update the control panel automatically. If you are installing for the first time, Apple has provided instructions here.