RedactorStyles Plugin Not Working
Craft 2.3 upgraded Redactor to version 10, which comes with a completely new API for plugins. This broke RedactorStyles which relied on the old API.

I've updated the plugin now, so downloading version 0.3 should make it work with Craft 2.3. Beware that the plugin isn't 100% backwards compatible, due to changes in Redactor and its API, so read the docs.