Answering for my work inbox (84), because the question doesn't make much sense for my home inbox (2726) because it's GMail and it uses tags rather than folders, so I never really move anything out of my inbox.
For me personally, it's helping me spend less time hunting for things I still need to do, and more time just getting them done. I find it far less stressful to only see in my inbox(es) the emails that still require action of some kind.
no subject
I'm not sure I get the point of Inbox Zero.
What's the point?