Been playing around with Overtone tonight, and while tidal's support of dirt is nice, Overtone has freesound support, which is also pretty nice. But what Overtone lacks is tidal's notions of patterns. Tidal patterns are just so immediate for defining rhythm. I'm having a little more trouble using them for melody and harmony, but I suppose that'll be my next challenge.
I'm also pretty excited to try gibberwocky, but once you drag Ableton into it, it doesn't really qualify as "forum music" any longer.