In contrast, Oracle's database upgrade agent (DBUA, graphical Java app) will perform an upgrade in place, usually taking less than 30 minutes.

The one place where I've found DBUA to fail is an upgrade of a 32-bit database to 64-bit (version 11.2.0.4 was the last offered for 32-bit). This type of upgrade requires the command-line dbupgrade utility, and it's a bit more complex.

Complete export/import is only required when switching architectures for Oracle. Postgres should try for this sometime.

I've also seen MS SQL Server quietly upgrade an imported database.