First off, great tutorial. People need to know about this stuff. There are a few things that I don't agree with in your post though or just don't prefer to use. Everyone uses VOIP in a different way. 





You don't need a 2.3 rom to make VOIP calls. Only to use the integrated sip stack in the 2.3 roms. I also do not like sipdroid. It's heavy on the battery and doesn't allow for more than 2 sip accounts. I use csipsimple instead. I have only used voip for all my calling needs.



You also do NOT need pbxes.org. Using this service is just like adding lag to your VOIP calls. It's another destination that your call must be routed though before it gets to you. 



My setup is, google voice > gizmo5 or ipkall (depending on where I am and what I am doing. I prefer gizmo but it doesn't always work.) > csipsimple with gizmo5, ekiga, and my asterisk server accounts. I use an app called GVoicecallback which works like the google voice app where it intercepts the number dialed and asks you if you want to have google voice call you back. I have this app setup to intercept ALL calls. I've also disabled the intercept in csipsimple and googlevoice apps. So when I make a call, google voice  calls me back at either my gizmo account or ipkall though my asterisk server. I also have my asterisk box setup so that if people call my ipkall number directly they are dumped into a conference room where everyone can just chat for a while.



Here is my old tutorial when I used sipdroid:old ipkall setup

Here is my tutorial on setting up your asterisk server for just one simple conference room: asterisk