The hardest part I've heard is to get the clothing mesh computations for self collision parts like the underarms and places where it bends and folds like knees and elbows. I'd be interested in hearing a little bit more on how does Poser simulations compares with the available plugins for Max and Maya, but of course we will have to wait until it comes out. If they do a good work this can be an area to raise eyebrows and start gaining some respect as a professional software package.