I've spent the day trying to process variours RSS feeds using XSLT and
pretty much decided it's not worth it...  Some feeds are ok, some
contain escaped markup and other contain a mix of escaped and
non-escaped markup, cdata sections etc

Those containing a seemingly unpredictable mix of escaped and
non-escaped markup are probably not worth the effort to fine-tune
the XSLT accordingly.

When the order is predictable, I've simply used d-o-e, although it is
certainly evil.

<xsl:template match="rss/channel/item[ content:encoded ]">
  ...
  <xsl:value-of select="content:encoded" disable-output-escaping="yes"/>