You've got to fight off both by blending offerings from both. Use the cash raised in the most current IPO to bring value back to your PSTN-grade consumer services. Deliver a service with the simplicity of the telephone and capabilities of the Internet.
1. Offer a Phone Trade-in Program ??? Part of the limitation of Vonage's service is that plain old analog telephones are rotten platforms for delivering rich services. Soft-phones (more on those later) will help you leverage the PC better, but that hasn't been your market, has it? You wanted to give a service that even Mom and Dads would buy, right? But now you need teen as well. So why don't you offer a trade-in or upgrade program for customers to exchange their analog phones for a high-end phone. Whatever you offer, bundle in a value-add service, charge them an upgrade fee, and you'll transform the product delivery potential of your servcie. Heck, you could probably resell both of those components, or give them to a non-profit as a tax write-off and make a profit on its own.
2. Develop a "Vonage Certified" Service ??? It's been a wonder to those of us who've watched the rise of Vonage as to why the company hasn't taken advantage of its SIP-compatibility. Limiting customers to just telephones ignores the fundamental differentiator of Vonage. Open up your service to every telephone, soft-phone, video mixers, gizmo, and SIP software on the planet. Create a " Vonage Tested" program and use your formidable marketing engine and customer base to push those products out to the masses. Evangelize "rich communications" the way Vonage evangelized Internet telephony.