I've used it a couple times. Most of the hubs won't let you on unless you share a really large amount of files (30Gigs or more is common). Because of this you get a lot of tools sharing multiple copies of the same thing, their C:\windows directory, installed programs, etc. Because it does use hubs it is seems to be faster than the various gnutella networks, but won't have as many files available from any one hub.

-Mike