I successfully installed PP on my OBI110. The issue is many times when I call my PP number directly, I immediately get message that XXX number(my PP number) can't take your call now. Obviously my OBI doesn't ring. I chatted with PP a few times, and they checked my OBI settings, and everything looks Ok. I would say that 60-70% of my incoming calls fail.
The PP is the only one installed on my OBI as SP1.
For future similar posts, the "North American ITSPs - Including Google Voice, Skype, etc." forum would be more relevant. I don't know how PhonePower works.