Complex Features in GeoServer
GeoServer has released a 2nd Beta of version 2.0. You can read about it on their blog.
This is exciting because they've introduced what they're calling the "app-schema extension". Essentially, it represents real support for complex features. This will open the door to GeoSciML delivery through the friendly GeoServer interface.
Unfortunately, I haven't been able to download the new beta yet - there seemed to be some problems with their mirrors at SourceForge... However there is even documentation for the app-schema extension located here.
Hopefully in the next couple of days I'll be able to start digging into this.