<p>Other than Visual Studio, what tool have you found best to create, edit, maintain, and possibly debug your XSLT files?</p>

<p>I work on a fairly big project and we have tons of XSLT files and they have grown quite complex in their implementation.</p>

<p>The language seems so brittle. It would be nice to navigate and identify errors more quickly.</p>

Liquid XML Studio
is pretty good at real-time interpretation of your XPATH queries.
Cooktop
also lets me run my XPATH queries and shows me the XML and HTML generated by running the XSLT against a given XML.
Also, a colleague tells me that newer versions of
Adobe Dreamweaver
allows you to associate an XML file with an XSLT file and run the transformation.
Whenever possible i use
Subversion
for change-tracking.
And for navigation, i most often use
VIM
(or
VIEmu
) and sometimes a custom Visual Studio extension that builds an index of the current document's xsl:template and xsl:variable nodes to provide one-click navigation to the root entries.