Vince, thanks for the quick response. What about an instance where all versions are 10. ArcGIS Desktop is then updated to v10.1. From desktop, the sde geodatabase is upgraded to v10.1 which would still leave ArcSDE at v10.
No, after you upgrade the geodatabase, the SDE is at that level. If you have an application service, and you fail to delete and recreate it, that's an error.
Ok, so with the scenario I presented, an sde service would need to be recreated, understood. Direct connect should work fine though (after upgrading the geodatabase to v10.1 using desktopv10.1), right.
Views are just views; there's nothing release-specific about a view. Any necessary changes would either happen to the underlying ST_GEOMETRY object, or to the base table's triggers.