I've been using Pd as a sound environment, generating midi as well as generating sounds, although more of the former than the latter. The main reason for that was that I didn't really have a useful way of getting sound to and from Pd - but I do now, with Soundflower which I don't know why it took till now for me to find.
Add to that the Percolate binaries I just found for Os X - with a lot of granular synth instruments and I have a ton of great new reasons to work with Pd.