I am using the IRB with Skype. It does work, but uses quite a lot of CPU on a fast machine (30% on a 2.66 GHz Intel Core 2 Duo).
Also I am not particularly fond of routing other people's calls as Skype does.
Is there any other way to use sound, both listening and modulating via the internet?
Like VoIP, iChat or such?
(Working on Mac OS X, with W4MQ running under Parallels and Windows XP SP3 - works well, also Skype under Mac OS X)