A quick post to pass along that a new version of the Lync client for the iPhone is available. This update resolves the issue where multiple push notification would occur for a single IM under specific circumstances (listed in the associated KB article below).
The updated iPhone client is available on the iTunes AppStore here: http://itunes.apple.com/us/app/microsoft-lync-2010-for-iphone/id484293461?mt=8.
The corresponding KB article is here: http://support.microsoft.com/kb/2728915.
Note: users should sign-out of the Lync application before applying the update. This will avoid abnormal termination of the Lync session.