Group Chat Stress has released as part new tools within the Adoption and Training Kit.
You can use the Group Chat Stress package to help verify your Microsoft Lync Server 2010 and Microsoft Lync Server 2010 Group Chat hardware deployment. Group Chat Stress is made up of two applications: Group Chat Stress Tool, a UI application, and Group Chat Loaders, the stress engine (which has no UI). Use Group Chat Stress Tool to create the configuration files for the loaders and to distribute the binaries to the remote machines that will be running the loaders. Use Group Chat Loaders to apply the specified load parameters on the Group Chat Server.
I haven’t loaded this up in my lab yet but remember this is a tool to stress Group Chat components, there is a separate download for the tools to stress Lync Server - http://www.microsoft.com/downloads/en/details.aspx?FamilyID=94b5f191-6d80-4dec-94c2-fca57995f8b7
(removing term Power Pack from title and content due to confusion with Quest tools)