Vonage Phone Service

I've seen a lot off adds lately pushing this VoIP phone service.
http://www.internetphonesoftware.com/vonage.html

Has anyone dealt with or use this service and is it decent quality wise as regular phone service's like ATT and Sprint?

Thanks for any comments.

I used it about a year ago. It was way too erratic for my taste so I ditched it. I hear it's better now than it was, but i'm going to wait and see how it matures before considering it again.

I think the VoIP technology needs to mature more before it can be a viable option. Most cellphone plans are cheaper than VoIP and don't have any hiccups. The only time I can see it being useful is maybe if you make a lot of international calls. Even then there are free solutions such as skype that are better provided both parties have computers.

It's worth keeping tabs on though. Some of the major companies are starting to get behind it. Once it beomes more mainstream, it will mature. Right now, it's just not as reliable as it should be.