comp.dcom.telecom and comp.dcom.xdsl may be good groups for more insights

LB

You can't get VoiceWIng or DSL without a Verizon land line first. You can
get Voicewing with a cable modem and have that as your "home phone".
Voicewing is not as good and is more expensive than Vonage. Vonage has top
quality, free calling to Canada (VZ charges .02/min). Other features are
similar, but Voicewing is anywhere from 5 to 10 bucks a month more than
Vonage (depending on your VZ package discount). Skip Voicewing and go with
something else. No matter what you get for Voip, though, you still have to
have a Verizon landline phone if you are going to use Verizon DSL.
BTW-I have Vonage. Great service. There are cheaper options, but none match
Vonage for quality, not even VZ.

Well, you can use VoIP with cable modem service, too.

Keep in mind that VoIP will not work during a power failure, and 911
service has been problematic.

What I do is have my landline with plain flat-rate local service for
around $17 per month (including all taxes/fees), and I use my cell phone
for all toll calls.  For me, this is much cheaper than VoIP, and I get
the much more reliable landline 911 service.