Within CTP6 and RC0, there is a bug based around enabling filestream. Within the setup process, there is a tab which allows you to enable filestream as it is disabled by default. If you happen to miss that dialog and process in the installer you will have trouble enabling filestream via the sql configuration manager. In fact, on the properties dialog, after enabling FS the OK button does nothing.
The team have now wrote a blog post explain this: Enabling FILESTREAM post SQL2008 Setup – a Known Issue in SQL Config Manager
The solution is to run a WMI script (available on CodePlex – http://www.codeplex.com/SQLSrvEngine/Wiki/View.aspx?title=FileStreamEnable&referringTitle=Home)from the console . To do this:
2) Execute the vbs script (cscript filestream_enable.vbs /Machine:. /Instance:(local) /Level:3 /Share:MSSQLSERVER)
File stream should now be enabled. Hopefully this will be fixed for RTM.