One of the limitations I've put on this Fate campaign - really the only D&D staple that I'm disallowing - is that there is no magic in the world, and the Gods (if they exist) do not make their presence felt in daily life.
By and large that's not a major mechanical issue - you still hit things with swords the same way, and a religious character's motivations won't even change that much. It's just that his chosen deity isn't going to directly smite targets as a result.
But where it's led me to something of a dead end is in dungeons.
In your typical fantasy setting, an ancient temple or crypt is a tempting target for a PC of any alignment - magical items and the chance to slay a lich are tough rewards to pass up, whether you want to rid the world of his evil or steal it for yourself.
Without that supernatural element, it's proving difficult to find realistic non-meta reasons for these crypts even existing in the first place, let alone motivating players to bother delving into a mineshaft for the promise of... money? Being nice people?
In the end, money's probably going to have to suffice as a carrot on the campaign stick, at least to begin with. I'm hoping this experiment lasts long enough for the stakes to get raised a bit, giving the characters less self-absorbed reasons to get into the spirit of things.