It's faster, tho not always (if it's going to load, it's faster than).
That's what Kilari told me, about eg. putting wikipedia on Slimweb:
I just found a way to put the entire Wikipedia on Slimweb (at least almost all of it) in such a way that no one has to seed the entire wikipedia dump.
It works by having a mirror of Wikipedia where it is designed such that every person browsing the page in the normal way also seeds the article he/she is reading.
In fact this system can be extended to put large data stores onto this in a fragmented way while providing a way to actually prove that the content wasn't tampered with.
In a way it is like all the people with free internet access are collectively helping people with limited internet access by simply minding their own bussiness.