I found this information at the cover of the great, Heiko Boeck's book: NetBeans Platform 6 - Rich-Client-Entwicklung mit Java. It seems like Heiko's job was the migration of existing enterprise apps to Netbeans RCP. The book is based on his experience. This (German) book is, in its depth, comparable with the English Rich Client Programming, w. CD-ROM: Plugging into the NetBeans Platform.
However topics like migration from Eclipse to Netbeans are covered as well. I didn't read it completely, but Heiko really well explains the critical points of the Netbeans RCP development so far. Not only ProSieben, but many other companies are switching to Netbeans. It is really taking off. This is remarkable for Germany - actually an Eclipse land.