by support OS X you mean does thier management software run on a MAC? good question.
Tell me what your goals are, car set up, your budget is, who is going to tune it, and your experience with ecus, and I can make a recommendations.
The more exposure I get to it, the more I think the Hydra is a good fit for most tuners. Very robust, good visability, easy to tune, and good miata specific support.
I've also tuned AEMs, Links, TEC 2s, and a Haltech in miatas. I've also had some motec exposure in other cars if you have a endless budget.
