I use it, but it's actually the integration between Max and the Jit physics engine that they upgraded in the 6.0 release. It's like making a live music application with a live performance. I know some people use Quartz for this as well, but I don't know much about it and I don't know if you can program it to respond to audio generated signals to give specific movements and feedback.
Outside of live performances or performances using Wii controllers, Kinect, or other externals, not really. Creating your own filters and instruments is great for learning or for experimenting, but I know my instruments and patches are crappy compared to almost anything a professional studio makes. If I really understood how to make beautiful timbres, instruments, effects, and a better understanding of how to make that in Max, perhaps I'd integrate it better into the Live workflow.