I had been running SQL Server Express 2005 and was appropriately using SQL Server Management Studio Express with it.
I upgraded using "SQL Server Express 2008 with Tools", but the management studio express appropriate to SQL Server Express 2008 is not present. The old 2005 version is still around under the SQL Server Express 2005 folders, but no new management studio that can run with 2008 is present.
What do I need to do?
I think I found my answer so I might as well post my findings for anyone else who runs into this issue.
Uninstall the SQL Server Express 2005 tools (incl. SQL Server Management Studio 2005 Express)
Then in the SQL Server Express 2008 installation center, the first choice reads...
"New SQL Server stand-alone installation or add features to an existing installation"
Well, I didn't want to create a new installation, but I do want the new features
BTW, the option further down below on the center...
Upgrade from SQL Server 2000 or SQL Server 2005
does not install the management studio tools for 2008.