Symtex said:
- no phone when your internet is down
- no phone when you have no electricity
- Fax, alarm system or any other devices that requires an analogue line (PSTN) won't work with VoIP
- Limited 911 service
In terms of quality, it depends on which codec your provider is using. Most VoIP provider used G.711 or G.729 which has a respectable voice quality.
I agree with all of these points except that alarm systems won't work. We have an alarm system and checked into using it with VoIP a couple of weeks ago, and they confirmed that it would work.
Of course, that still is predicated on the fact that you have power, which is something that could be accomplished with a relatively inexpensive UPS system on the router/VoIP box.
Note that many people run exclusively with cordless phones - these won't work in a power outage either, so keep a corded phone handy for those situations.
Or, of course, just use your cell phone.
Also note that new legislation requires that by this fall (I believe that's the time frame), all VoIP services must provide 911 access on par with land lines.
