For a *long* time, whenever I spent time with C# customers, I would invariably get asked, "How do I create docs for my assemblies?".
And my best answer was either, "there's a XSLT file that makes the XML look a little better" or "you might want to consider NDoc".
Neither of which was a great answer. The XSLT was quite inferior to what people wanted, and NDoc also had limitations.
That issue was not unnoticed inside MS, but it's taken a while to address it, and I was otherwise occupied at the time, so I didn't notice it.
Kudos to the Sandcastle folks.