If I had it to do over again, I'd probably not have included dwarves or elves in my Dwimmermount campaign. It's not that I really object to their presence -- this is a D&D campaign, after all -- but, as the sessions add up, I find that certain elements of the setting would probably have worked better if humans were the only playable races. For example, death, dying, and the quest for immortality have all become important elements of the campaign, with the the appeal of the cult of Turms Termax being at least partly based on its promise of eternal life to its elite members. But the lengthy lifespans of demihuman races undercut the cult's appeal somewhat, even if neither dwarves nor elves are truly immortal.
Now, as I always do, I've begun thinking about ways to address this within the campaign setting and the result might, in the end, be more satisfying than the straightforward approach I could have adopted in a human-only setting. Still, there's little question that it would have been simpler (and truer to my inspirations) if I'd ditched demihumans at the start. On the other hand, part of what makes D&D the game that it is is its selection of playable demihuman races. You can get rid of them or replace them with others, of course, but, the more you change that "starting lineup," the farther you drift away from the peculiar kind of fantasy D&D evokes. So, there's a balance to be struck, I guess, between leaving too much unchanged for tradition's sake and changing so much that the result is unrecognizable.
More food for thought, I guess.