Back 8 or 9 years ago I architected and worked on a team to write a very large and feature-rich application that depended on XSLT for a ton of UI-deriving functionality.
I found it extremely powerful.
I have never used it again, because the power it afforded me was not worth the heartache.
Just prior to .NET I worked on a classic ASP project that did this - the view models were basically SQL queries with 'FOR XML AUTO' and the 'views' were XSLT stylesheets.
For getting simple data up on a web page it was fantastic. But for more complex stuff it got wickedly complicated to maintain at an exponential rate. XSLT just didn't scale (and/or we just weren't good enough at it to make it scale).
I found it extremely powerful.
I have never used it again, because the power it afforded me was not worth the heartache.