I'm working on finishing the EOAdaptor for XStreamDB, and one route I'm exploring is taking the source XML from XStreamDB, running it through DOM and then into full EOs. I've been playing around with DOM libraries, and just checked out the latest beta of dom4j.
It's evolved into one sweet library - basically takes the standard Document model, and wraps XPath, XSLT and other goodness around it. They're even working on adding schema and validation support (which will be very handy for anyone creating XML documents on the fly. Like, say, in APOLLO...
I've just modified a sandbox copy of our Teaching Resources application to use dom4j, and it's quite fast, too. It only takes about 2ms to parse a full IMS LOM record into a Document. When tied with the EOF caching stuff, that is totally acceptable (depending on what additional overhead is required to get it into EOs, that is...)