I've only just picked up Spriter and i'm still getting to grips with it. So far it seems to offer me exactly the kind of features i'm after without the bloat that you get in other packages.
One thing I was wondering about is whether you had any plans to support vector graphics in future? That way I could scale the components of my character without losing image quality. I currently create base images in Inkscape. Then, to use in Spriter, I export as png. Finally I export the animation frames as png from Spriter. Perhaps not the best workflow but i'm pretty new to all of this.
Just to be clear, i'm not suggesting you include the drawing tools in spriter to create the images. I actually quite like the split between tools.
Anyway I haven't bought in yet, most likely will soon, keep up the good work.