Last week I installed an Office 2010 KMS server. I had to install it on top of an existing Windows 7 KMS server. So I downloaded the Office 2010 KMS host license pack and activated the machine. No issues so far. After I installed Visio 2010 on my machine I saw that i had installed and activated a premium version.
Visio 2010 comes preinstalled with a Premium KMS client key. Remember to enter the appropriate KMS key as needed in your image. See also http://technet.microsoft.com/en-us/library/ee624357.aspx