I am wondering about the hash quality and the hash stability produced by the String.GetHashCode() implementation in .NET?
I know that this isn't really included the meanings of quality and stability that you specified, but it's worth being aware that hashing extremely large strings can produce an OutOfMemoryException.
https://connect.microsoft.com/VisualStudio/feedback/details/517457/stringcomparers-gethashcode-string-throws-outofmemoryexception-with-plenty-of-ram-available