Voicemail on my cell has always been disabled, and VOIPo is set to 4 rings. When I call my VOIPo line from my wife's cell with simul ring to my cell, my logs show around 25 calls from my wife's cell to my cell (or perhaps vice versa) within about a minute and a half.

What seems to be happening is that the call forwarded from my cell is being simultaneously rung back TO my cell in an endless loop. If it works this way for everybody, I'll wait until Simul Ring is out of Alpha. If not, I'll put in a ticket.