The current beta version (1.5.3.1) runs quite stable now under Linux and Mono. I'm using Ubuntu-Desktop and a self compiled Mono 2.4. It should be more or less the same on other Linux distributions. Only a few glitches and small problems are left it seems, no big crashes.

My old Mac isn't working at the moment, so i've no idea if it works on MacOS-X too. In theory, it should ....