Annoying documentation niglets
Well, I've been working with a partial Roller 4.0 install for the last several weeks while I tried to figure out why the planet aggregator would not work. I didn't get much help from the dl, since my problem was "bizarre". I should have known that this was a synonym for "you missed something so basic we can't recognize the problem".
It turns out that I had the config entry to enable the planet aggregator in the wrong properties file. Despite the effort to make Roller 4.0 simpler to install, there are still issues. In particular, the user documentation specifies only one properties file (roller-custom.properties). There is a bug documented that the planet aggregator actually requires its own properties file with some duplicated entries (e.g. the database connection configuration entries). I assumed that the setting that indicated that the planet aggregator was enabled belonged in this file; it turns out it needs to be in the roller-custom.properties file.
Now that I am past this little niglet, hopefully the rest of the roller 4.0 experience will be good.