The biggest advantage, by far, is that the adventures are not necessarily tied to level - that they can be scaled on the fly. I can say that the NPC/Monster system is pretty darned awesome.

I like being able to pit a second level party against a giant and not have to worry that it will all end in tears. And because of the way NPCs work they scale relative to the PCs - so an NPC that can clean their clocks at first level can still do so at level ten.
For the homebrew in particular it means that I can scale an adventure when the PCs get to it - kind of important since it is a fairly open setting in regards to where they go. This allows me to place some adventures by area, rather than having them travel from job to job, adventure to adventure.