VOIP is great - Vonage is outstanding - no I don't work for them, nor do I receive any compensation for these comments
I've had experience with 2 separate VOIP companies: Lingo and Vonage. Lingo was spotty. I didn't think I would care that my phone was up just 98% of the time. However, that 2% is a big deal when you're trying to make a phone call and the line is dead. Granted, that was 4 years ago - but I probably wouldn't go back because of my experience. A friend of mine works for Lingo. He agrees with me about them.
Vonage is excellent. We've got good power here, so I don't usually deal with that issue. It's reliable, unlimited long distance, and cheap ($31 with tax). Ma Bell doesn't overcharge me anymore - I'm a happy VOIP convert.