I've had Vonage since March of 05. Here is my 2 cents:
I've had 2 internet outages in the last 5 years so reliability is not a factor for me. I also have my cell phone as backup. I'm satisfied with the voice quality. Their phone customer service is horrible (at least an hour wait for every call) However, they respond to email almost immediately. The number transfer took 3 months to complete but they (Vonage) gave me free service until it was completed. All in all I'd say that I'm happy that I made the switch. My phone bill is a faction of what it used to be.

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2003 3.0i White/Black 5 speed Manual.
Options: PP, SP, DSP, NAV, XENON.
Mods: Aluminum Running Boards, 4.6 Body Kit, 20" Style 132 Wheels, Eisenmann Sport Exhaust with Oval tips, Aluminum pedals, Xenonmatch Fogs, M3 Steering Wheel.

Can I have a sip of that HATERADE you're chuggin?