Firekraker, I share your disappointment that the Windows Phone version of Photosynth's mobile pano app wasn't ready for the launch of Windows Phone 7.5.
Although no one on the Photosynth team has directly answered the question of what day the Windows Phone version of the app will release, the original release trailer for the mobile app specifically said "Coming next for Windows Phone" ( http://www.youtube.com/watch?v=6BbuPPOVXQo&t=2m ) and here on the forums on a topic where people were begging for an Android version, Tony Ernst (from the Photosynth team) stated 4 months ago:
"Hey everyone, just wanted to give you all a heads up. We're hard at work on an update to the iPhone App, a WP7 version is next. We can see the value of an Android version, but our team is only large enough to work on one platform at a time.
Tony". (Source: http://photosynth.net/discussion.aspx?cat=01b6f15f-42eb-49cb-a221-ed56615e1c47&dis=785e0efb-9dac-4bb5-9970-6dad40785829 )