Curious to know if anyone here has any experience using a VOIP phone line instead of a traditional landline?

I've been looking into them and they seem a lot cheaper than a normal phone, and have some kinda cool benefits. I'm curious for some feedback though--I'm looking at Lingo, Vonage, and SunRocket mainly, though am open to other options. Really my bottom line is price and international calling, as I don't use my phone for much other than ordering the odd pizza and calling overseas.