I've played through the demo about 4 or 5 times and can easily say that the combat is one of the most challenging and robust systems I've played in a long long time. I'm picking this game up launch week because I support everything that this game stands for - I love JRPGs and Ghibli, and this seems to be a perfect mash up of the two. I highly recommend you at LEAST play the demo and experience this game for yourself.
Who else plans to pick this game up in a month and what are you looking forward to from this game? The prospect of each familiar playing such a different role and having it's own unique skills is the most tempting to me. I also foresee a really great Ghilbli story from this.
Late January cannot come faster!