kentopians

I have been using this device for the past 5 years. My use is simple... basic telephone service for the least amount possible.
My old land-line vendor charged me in the $80/mo area for, what I consider, basic service. They include (I did not have a choice) 30 min of long distance (included intra-LATA).
My issue was usage. All I really needed was a phone that I could use as needed. I did my research, compared it and the nearest competitor (which, I think is a few dollars a year cheaper but the reviews at that time complained about support) and choose NetTalk.
Occasionally, my cable company decides to do maintenance (at any time) or their local hub gets knocked out by weather and when cable service is restored my DUO comes back with a flashing red or green light. In the beginning I got on line and looked through the FAQ and found that all I had to do (just like a computer) is go through a power down/restart. Much like the CTL-ALT-DEL. And, viola, the much welcomed single ring telling me the device is back on line. I could go on but you get the drift. And for those that need a more verbose power down/restart for the DUO... after your ISP has finished, unplug the power and disconnect the cable to your router... wait a few seconds... connect the power and then the cable to the router. You should see a red, then flashing green and finally solid green and then... wait for it... the single ring. If this doesn't get you back on line, do the above and before reconnecting, recycle your network equipment (router and cable company device).
Once, I did talk to a support person and found him to be patient and helpful. Understand, I only have called once in the past 5 years.
I like the device enough to buy 2 more when they were offered as a promo prior to the introduction of the next gen of the product. Now, I have one for home phone use and another for my all-in-one home network printer. I have faxed many times without issue.
If I had to complain, I would say that sometimes connection is bad. The fix is hang up and redial. You have to remember, this is VoIP (voice over IP) and heavy network traffic can be a villain. Maybe if the vendor made available a more sophisticated device.... oh, but then it would cost more... never mind (just being sarcastic).
I'm sure all these other folks have valid concerns or issues with their devices... fortunately for me, since someone in my family kissed the Blarney Stone, I haven't had any issues.
This device has its limits. If you must live on the "bleeding edge", go buy Cisco (or another commercial grade product) and pay for the move advanced technology.
I hope this helps