I don't think so, but it depends what you expect from a POTS line. None are as reliable as POTS, both because they depend on your ISP, and router all working, and because they all have the occasional flakeout. (Phone companies have spent the past 130 years learning how to make phones reliable, so it's not surprising that it's taking a while for VoIP to catch up.) Other than Packet8, none of them offer real 911, so you'd best have a cell phone for emergencies that you keep charged and working.
I dumped Vonage in favor of Lingo earlier this year when the call quality became unusable and their customer service turned out to consist of a 24/7 busy signal. Lingo's been OK, call quality and reliability are decent, support is OK. My only complaint so far is that through some screwup, a call to Argentina that I know was about one minute was billed as 3 1/2 hours. They reduced it somewhat, but not as much as I'd like. But since the rate was only 4 cpm, the actual amount at issue was on the order of two bucks.
I have a web page at
R's,
John