There has been considerable work on the Discussion Database over recent years, adding an XPage interface and a host of features. If you look at the R9 installs, you’ll see there is a version for 8.5.3 and another for R9.
But you need to be careful if you have upgraded a server to 9.0.1 because there are additional changes. The bigger problem is that the version number of the template has not been changed. So there is no ostensible difference between the 9.0 template and the 9.0.1 template until you compare them in Domino Designer or try to run the latter on a 9.0 server. At that point, you get an error because the deviceBean is not available, it was a new bean in the Extension Library for 9.0.1 (thanks to Ulrich Krause for blogging that and helping me swiftly identify the cause of my problem!).
