No doubt about it. It caused major problems for me.
What this proves is that Vonage is simply not a viable replacement for wireline service. I've been a Vonage user from the beginning, suffering through echos and quality issues for the first several months.
I figured it was all worth it for the unlimited, inexpensive "out WATS." But, now that SBC offers unlimited nation-wide toll for a competitive price, it makes me think about using only my wireline (which I never got rid of). The only advantage Vonage offers today are virtual numbers.