These threads started because of some confusion around one of our MSDN docs – specifically this one on migrating code to XslCompiledTransform. Specifically it says:
The XslCompiledTransform class includes many performance improvements. The new XSLT processor compiles the XSLT style sheet down to a common intermediate format, similar to what the common language runtime (CLR) does for other programming languages. Once the style sheet is compiled, it can be cached and reused.
Implying that the style sheet was what needed to be cached and reused. This is a documentation bug and is in the process of being replaced. The only supported way to cache and reuse compiled XSL stylesheets is by caching and reusing the XslCompiledTransform object.
So there’s the good word. Eventually we’ll see it updated in the docs, but that is my experience, and what I tell my customers on-site.