Try the USGS MP Metadata Translator. I somehow missed it earlier, but it's producing all of the various HTML I'm familiar with.
I haven't had much luck with the XSLT Transformation Tool. In fact, no luck. But I'm an ArcGIS 10 client w/ ArcGIS Server 9.3.1.
I had filed an ESRI incident for a problem with the arcpy.ExportMetadata_conversion, so maybe they are all related. It sounds like there's a lot of metadata issues @ ArcGIS 10, so I haven't and won't spend a lot of time with ArcGIS 10 metadata until SP1 (or maybe SP2).
So far, I've been exporting to XML and then using msxsl.exe to process the XML with an XSL file from 9.3.
Here's an example of processing XML to HTML w/ a 9.3 FGDC FAQ XSL (that I copied from an existing 9.3 install--might be good to keep a copy of those handy on a usb drive):
msxsl wp_meta.xml "c:\temp\FGDC FAQ.xsl" -o wp_meta.html -u 3.0
It's not perfect but the xsl can always be tweaked to produce the HTML that you are after.