Thanks a lot for those tips. I feel a little bit safer now. :-)
I get a lot of telemarketing calls - in fact, that's my primary reason to get this, so I can have more control over the phone. But I don't think blocking by callerID will work, because they change them at will, and it's like trying to get rid of flies outside with a fly swatter. Instead, I plan to use IVR to add a little simple interaction with incoming calls, like pressing one key to connect, another to leave voicemail, etc. That way, robocallers will disconnect, and most telemarketers won't even hear the first part of the message anyway. The others I can deal with - I'll just tell them not interested, please remove me.