I just noticed release of the Eclipse, WTP (Web Tools Platform) 3.2M4 milestone (released on, December 11th, 2009). The WTP Source Editing release, in WTP 3.2M4 milestone, includes an enhanced PsychoPath XPath 2.0 engine.
Xerces-J users using the XSD 1.1 support (specifically XSD 1.1 assertions and CTA/type alternatives), can use the latest PsychoPath library from http://www.eclipse.org/webtools/. The latest development PsychoPath library can also be downloaded, from https://build.eclipse.org/hudson/view/WTP/job/cbi-wtp-wst.xsl.psychopath/.
Dave Carver, has been doing a great job in putting this all together.