Poser 4 runs okay in Classic mode. There are plenty of alternatives to Poser for creating humans, but they're a lot more expensive and time-consuming. You can build some great human models in Maya, for example, but it's far more convenient to use the ready-made models in Poser. That said, DAZ 3D is working on a Poser-like program that will support Poser 4 products. No word yet on when it will be out, for Mac OS X or otherwise. I don't think they've said anything about a Mac version, but I bought Mimic from them, and it runs natively in OS X, which is a good sign.