I can't help you with the disadvantages, but my wife gives them a six sigma rating relative to reliability right up there with the ATM's. I have not been able to fault that line of thinking and continue to pay the 40 or so a month for her (can't get the word for it, you married guy's know) whatever.
We have had up to and including a hurricane and 28" of snow and when she picks up the phone she gets a dial tone. So we are keeping ours.
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If you fail to follow through, you will fail.