The one I wanted to ask about, though, is that the features have lots of extra attributes. For each attribute, there is an extra, null-valued attribute with the suffix .xsi_nil (e.g. "source" and "source.xsi_nil").
Why? Has anyone else encountered this? The WFS is being served from Geoserver v 2.1.2 and I'm using ArcGIS Desktop v 10 SP2.