We've upgraded DataPump from v9 to v10 - and are planning to upgrade to v11 in a few months. Everything posted on the Monarch forum is accurate - Utility will let you convert your .od files to .xmod files easily, same for .prj to .xprj. But If you're running v8 already that shouldn't be a problem.
The tricky bit will be migrating the processes that you have defined in DataPump v8. I'm assuming that you're running with DataPump connected to a SQL Server? The upgrade should work smoothly from v8 to v9, fvrom v9 to v10 etc, but I think you might want to ask Datawatch's own services department for confirmation that the installation routine for v11 of DataPump will pick up the processes from the SQL database.
There's a nice feature in v10 of DataPump that allows you to export all processes as an XML file, and then import them into another instance, which is helpful if you run a development environment next as well as a production environment and want to take a process from one to the other after testing.
Hope this helps,