I'm using Mac OSX 10.2.8. Tried X-Lite, Voiper, and several more. Mainly for tuning into group teleconferences that are organized through various conference calling companies. Express Talk has been the best, especially since this new upgrade. Earlier difficulties submitting access code. I've discovered that if I need to call back in to conference, because my 2 hour limit has been reached, there's about a 5 minute period before I can re-enter the access code. Otherwise, it's garbled by the receiving computer/phone system. This seems to be the case with all the softphones I've tried, Express-Talk being overall best.

Only complaint is that, unlike X-Lite, you can't change preferences while engaged, eg. from head-set to built-in mic. Records calls, and many features I haven't used, like 6 lines, transferring, hold, conference calling.