The clicking problem is related to the mixer Apple provide (which also has very high latency). I have been able to improve it by altering buffer sizes and some details of how the interface to the hardware is handled, but a better solution would be a half-decent mixer - happily, someone is currently beta testing one (Bob Lang at
www.mandolane.co.uk, who also provides the Java Midi interface required on the Mac). That mixer greatly improves things, though the REW software needs some tweaks to work properly with it, so you can't use it just yet. Only downside is it is an output mixer only, so there is still the problem that Apple's mixer only allows access to the built-in hardware for audio input, haven't found a solution for that yet.