One of the early design points is to make it easy for people to switch. For instance, make it easy for LJ and other system friends to read your posts, and for you to see theirs (that's easy, incorporate an aggregator, but should allow tag/person/friend-of-a-friend filtering etc). You ideally want a situation where while the full plan has everyone switching[1], it's at least a little bit better for one person. Eg. they can use LJ as easily as now, but have a more customisable and free interface with useful filter twiddles :)

[1] Though not exactly. I think it should be *distributed* so there will be many servers which people have accounts on, and can easily share posts between them. There are technical challenges, but then so are there in everything being run from LJ's servers. I realise I'm reinventing trackback, but it needs to be done :)