I only know of it from time spent on Dreamwidth; it's a lot bigger over there than it is on IJ.
I like it as kind of an informal way to talk plot-things, whether it's planning or flailing or whatever you're after. But like Jackie said, there's a lot of memes that go around and muse-prodding and tidbits of cr stuff happening. You can definitely use it to post your own threads-- like bingo or open things for people to comment on-- but if you're going for overall game effectiveness, you specifically could use it as an additional way to notify people of things that are happening, like an extra link to the Monday Meme and such.
Mostly just for having all the avenues of communication, really. I know I'm on there like...all the days, so.