If you really suspect your Obi, there is a simple and relatively simple set of tests.
Test your VOIP service at
http://myspeed.visualware.com/indexvoip.php or one of the other sites that determine your quality based upon ping, jitter, etc.
Second test, create a free Callcentric account and get a free NYC number. Configure your OBI to CC and receive some calls there. Turn of the GV chat and forward your calls to the Free NYC number. Compare and contrast calls into the GV number and the New York City number.Check quality, etc. If they all seem crappy, it is your internet, router and/or OBI.
Third test, if you want to swap out hardware (without much cost) go to Walmart and buy a $9.99 BasicTalk unit. It uses Vonage and the $9.99 payment includes 1 month free. If it works, you know your internet fine. If it doesn't work, take the unit back to Walmart for a refund.
If the Basic Talk unit works AND you want to use it with a different provider (like Callcentric or
Voip.Ms, etc) then you follow the simple instructions to zap the Vonage config and home it to another provider.
http://www.dslreports.com/forum/remark,28597028 Note that following that procedure does not reveal the Vonage credentials, it just erases them and allows you Admin access to set your own. Cost si $9.99 for the unit and whatever charges your VOIP service charges, since GV to OBI is going away as we have it now.