VoIP or Digital Home Phone Service

It seems that carriers are pushing VoIP hard with really nice features and seemingly low monthly fees. So, I got intrigued and looked into how it works to see if I might get the service. In our area, the to providers are Vonage (their ads are on TV all the time) and Comcast, with those funny commercials about how your phone conversations don't change, just the phone service.

My understanding is that first, you must have some kinda broadband internet service either through Cable or DSL. Which is fine, most of use seem to have that. For me though, it seems my DSL service isn't that reliable. I've come to expect to be able to use the home phone whenever I pick it up. However, with VoIP, if my DSL service isn't working, then I can't make a phone call neither. That's not good. Additionally, requiring the broadband service kinda takes away from the low prices that they are offering.

Also, it seems that connecting the phone to the cable/dsl modem also complicates things. Like the TV box for TVs. My parents and grandparents are able to use the TV fine with the Cable box. But by adding the box, that seems to somehow complicates how they watch TV. I wonder if the VoIP phone would have the same kind of complication for them.

Aside from those two "issues," it seems digital home phone service offers some great included features that we're accustomed to having for free with mobile phones, like call ID with Name, Call Waiting, voicemail, call forwarding, 3-way calling, and other convenient feature like that.

I'm kinda on the fence after looking at www.vonage.com and www.comcast.com. Does anyone have any experience with these services? Would you recommend it?