Like I said, I'm yet to finish boning up on what, exactly, Urbit is .. Sorry - not trying to be pedantic - but how is IPFS not a personal server? I can serve content with it right now, in fact - its what I mostly use it for at the moment.
I guess Urbit is more of an 'operating environment' that allows applications to be built, then?
Yes -- Urbit is a "server" in the sense of "computer," which you control and which runs your own apps.
IPFS stores and serves your data; so does Dropbox, Cloudflare, etc. In a sense the best way to see IPFS is as a distributed CDN, of course with an immutable namespace that actually works.
I guess Urbit is more of an 'operating environment' that allows applications to be built, then?