I am working on the QGIS workshop Tutorial for QGIS Plugin Builder and notice that it is for QGIS 1.1. As this seems like a popular tutorial, in general, what are some areas of this tutorial that need to be changed since the QGIS 2.0 release?
Doesn't sound like that's caused by the API changes.
Did you double-check that you didn't miss any step when creating the GUI, e.g.
change the name of the TextBrowser object to txtFeedback
The official documentation, which is kept up-to-date by the project team is http://documentation.qgis.org/2.0/en/docs/pyqgis_developer_cookbook/plugins.html