I use xfn, and find it useful

Yes to the first half, no to the second. Good idea, but not very useful in current practice.

OTOH, creating XFN markup is simple enough that it's easy enough to do it in the vain hope that, someday, someone will find it useful.

I'm a huge proponent of microformats, but no one can deny that we have to have some markup before anyone will build any cool apps. Chronos, almost all microformats are easy. Why not add votelinks, rel-tag and rel-license to your tool belt. Each one is a simple elemental microformat.

more to say. Think of microformats as progressive enhancements. We do this with CSS all the time. Base functionality is the same cross browsers, but the more contemporary browsers give the user a better experience. Slowly the other browsers will come up to speed but you won't have to change your markup. Think of microformats in much the same way.