Livebrush is interesting for a couple of reasons, not least among them that it seems to present a more intuitive and fluid way to work with vector brushwork than Illustrator.
Takes a bit of getting used to, though, because what dictates the width/strength of the lines isn't pressure, but speed. The faster I move my brush, the fatter the lines I get.
That being said, I am a total nub at this, so it's entirely possible that there's a way to adjust so that the lines respond to pressure, and not speed.
The program itself seems pretty nice in terms of responsiveness, and the kinds of lines that are generated. Especially nice is that for just US$10, I'll have the option to export the entire thing as vector shapes.
I'll probably play with this some more on my upcoming holiday.
I also find it interesting how adapting to / learning this new tool has resulted in something quite far (I think) from my usual linework... Omm!