I have working on a dynamic dress and made several cloth simulations that were going very fast until I finalized the material zones ( since I wanted the users to turn on/off transparenciy for short, elbow and long sleeves). Once I added those materials to the obj, simulation times went to a complete crawl( even with absolutely no texture maps loaded), so much so that I am going back to a single material for that dress.

Dominique Digital Cats Media