Just a quick note that might be useful to some.
If you publish a SQL Server (in this case 2014) table or view with a GUID field using GeoServer (version 2.10), it will fail to make a valid WFS because the &request=DescribeFeatureType response will not include these layers.
This manifests itself in various ways depending on the client, but in QGIS on trying to load the layer into the map we get this in the "Log Messages Panel":
Analysis of DescribeFeatureType response failed for url srsname='EPSG:27700' typename=xxx:yyyurl='https://mysite.com/myworkspace/wfs' version='1.0.0' table="" sql=: it is probably a schema for Complex Features
which had me puzzled for quite some time!
Changing the data source view to include this field with
CAST(myGUID AS varchar(36)) AS myGUID
then hitting "Reload feature type" in the GeoServer layer configuration screen fixes it. This changes the field data type from "UUID" to "string" in that screen. Or just omit the field entirely.
My guess is this will not help transactional WFS, but I have not tested this. Overall, GUIDs are still best avoided in GIS-land as they are so poorly supported by the database drivers.