This is information for Beta 2 - if you stumble across this in the future and have a ship version of VSTS please consider it expired and rotting so that it does not cause you more harm than good.  That said, and with the disclaimer that applies to all information on this blog, here's the best I've been able to find so far in terms of instructions for setting up permissions for VSTS:

http://blogs.msdn.com/vstsue/articles/422773.aspx 

Also be careful since there are multiple places you need to set up permissions (TF permissions are different from Sharepoint for example) as you will notice in this document.  Kind of like how setting Windows file share permissions can throw newbies off because you need to set them in two places (both sharing and the NTFS permissions).