Actually, until Google Voice fixes the longstanding bug where the Call Screening option is ignored on calls to a Google Chat destination (it is always on, no matter how you set it) it really will make no difference. When the OBi answers the call it immediately sends a DTMF 1 to get around that bug (you can turn that off in the OBi device settings if you really want to screen calls, but I think most people don't much care for that feature).