Since sdorn mentioned it, I thought I’d take a look at the Windows Live Writer. So far, I can see where people who use multiple blog services would like it, but as a Livejournal client, it seems to be lacking a bit.
I may play with it a while, but I’m not so far thinking it’ll replace SeMagic. For one thing, it doesn’t seem to have the options for specific LJ stuff like current music, mood, or usericons. Then again, I’ve only given it a cursory inspection.
EDIT: It doesn’t support LJ tags either. That doesn’t make it extremly useful in my mind for a Livejournal client. Too bad, it’s got a nice streamlined feel to it.