Irin is online again after a hiatus (available at http://www.carloscaires.com/). I saw a demo given by Horracio Vaggione at the June in Buffalo festival a couple of years ago. What I remember most about it is that it seemed to have a really good timeline interface. Horracio spoke extremely highly of the environment in serveral conversations I had with him.
Irin definitely has a fixed application (unlike Jamoma), but I believe it does what it is designed to do very well.