Our company seriously pursued using Spine for all of our in game 2D animations in small to medium sized budget projects. Unfortunately the runtime license was far to costly and restrictive to use for work for hire type client work, of which most of our work is. Really wish we could just pay a flat fee rather than cause all sorts of red tape and recurring payments for our clients. Most of the games we produce are for not for profits that can't really justify those kinds of recurring costs. Ultimately, we built our own tool that I'm sure is far more primitive but gets the job done.