Is there an equivalent of the System.IO.BufferedStream class for WinRT? The class itself isn't available, but is there a way to achieve the same behavior?
No, but you can use any of Windows Runtime streams with AsStream... extension methods. They create a "wrapper" streams that contain an internal buffer, and you can set its size. Refer to Stream performance in C# and Visual Basic section of Access the file system efficiently MSDN document.