From where I sat in Windows Security (I wrote much of the BitLocker UI) these are a couple of anecdotes:

I remember one of the base team architects laughing and bragging about how and why they killed managed code and banned it from the OS — the technical reasons where valid, but the attitude was toxic. I think most or all of the generation of architects that had come from DEC have now moved on, but they also took tribal knowledge with them. I wonder how much they were encouraged to find other things to do because of this type of attitude (which not all of them had btw)

Moving on

The Avalon team appeared to be drinking their own cool aid. They had charts on the wall showing their performance goals and progress. All the performance measurements on those charts were annotated as "estimated". I remember an internal alpha that had strong polynomial execution time based on the number of elements in the logical tree. It felt like the design was good, but that the correspondence of the implementation to the design was missing.

When Avalon was booted, we were told to write UI in a broken framework called DirectUI which had a convoluted history, an arrogant maintainer, and a weirdly mismatched documentation. Much was documented that wasn't implemented, the standard answer to missing features was "add it yourself", but if I pushed a code change to shell code (where it lived in the codebase) it would typically cause a forward integration from winsec to base to be rejected.

Good times