I have IIS 7.5 installed on Windows Server 2008 R2 and I have the Web Management Service configured to use Windows Authentication (including the WindowsAuthenticationEnabled registry key set to 1).
From another my workstation on the same domain as the IIS server I have the IIS 7.5 Management UI installed and I can connect to the IIS server by re-entering my current Windows credentials and then I can fully manage the IIS instance.
Also from my workstation I can run MSDeploy and specify to connect using WMSvc and NTLM authentication and I can perform deployment operations without being prompted to re-enter by current Windows credentials.
How can I configure my environment so the IIS Manager UI doesn't prompt for my existing credentials when connecting to a remote IIS server?
Try restricting accepted clients to windows authenticated users, by modifying the "Acceptable for unspecified clients" setting: http://learn.iis.net/page.aspx/158/remote-administration-for-iis-manager/#02