Thanks to a lady in our industry who contributed to my question on my personal VoIP by Association blog at http://suzanne.supertec.com, we now have a very cool comparison/contrast matrix of VoIP mobile applications! Take a look at http://suzanne.supertec.com/2008/10/response-to-my-request-to-compare.html and even download it.
It covers <a href="http://www.ebuddy.com">Ebuddy</a>, <a href="http://www.eqo.com">EQO</a>, <a href="http://www.gizmoproject.com">Gizmo</a>, <a href="http://www.fring.com">Fring</a>, <a href="http://www.mig33.com">Mig33</a>, <a href="http://www.nimbuzz.com">Nimbuzz</a>, <a href="http://www.skype.com">Skype</a>, and <a href="http://www.truphone.com">Truphone</a>.