Can ArcMap 9.3.1 consume ArcGIS Server 10 map services? I've recently been told ArcGIS Explorer 1500 is likely the only Esri product that can consume both AGS 9.3.1 and 10 map services. But I'm thinking that statement may only be true concerning ArcSDE geodatabases.
If ArcMap 9.3.1 can't consume ArcGIS Server 10 map services, then this would be a good argument for map services to be published with a version number. I've noticed Image Server provides a metadata item for a two-place image service version number. I don't see the same thing for a 9.3.1 map service. There is a Description field but no map service version number field.