Myrhdraak
Explorer
I've found that Scribus is easily 100x easier to use for more complicated layouts than any version of any Word Processor. Even the best of them simply lack the ability to frame up a page, create complex book layouts, etc.
The thing is, by the time you get to the point where you are wanting to do that, you've got to be pretty serious because its going to be a large time commitment, and then what? I've kinda gotten to that point with my own work, where its fun and whatnot, but laying out all 3-5 hundred pages of material in a complex format would be months of work, at best. Beyond which there's the skill question. I mean, laying out books is definitely not casual work! You borrowed heavily from the 4e layouts, which is cool, but for any of us who would desire to move beyond that it gets exponentially more difficult (or you have to just settle for something much less involved, which is OK too, lots of material out there is formatted in a very simple fashion).
As you say, it all depends on your ambitions. Do you intend to publish your own RPG book and make it attractive with a lot of graphics etc. it is not only a lot of work, it is very costly to get the licenses for the graphical content, etc. However, if your ambitions are to only make a nice printout of your own campaign in bookformat, then I think Word will do just fine.