I have not been there myself, but as we heard from those who attended XML 2007, there were quite a few talks mentioning eXist:
Erik Bruchez: XForms and the eXist XML database: a perfect couple
Dan McCreary: Using XForms and eXist to Manage Metadata
Kurt Cagle: Lightweight XML
Mark Birbeck: XForms, XHTML, and RDFa for Internet-Facing Applications
Mark Birbeck: XForms on the Desktop using Sidewinder
The slides for the first two talks are available online. We also heard Norm Walsh mentioned an XProc implementation in XQuery based on eXist (I guess this must be Jim Fuller's XProcXQ). XProc is an interesting new standard and I would love to see a simple implementation which can be easily integrated with eXist.