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I, too, was looking for a PDA/cell phone combination, so I purchased the QCP6035 from Kyocera. I lived with it for a few months before writing this review, which in a nutshell is: good software, but too big.
I've had Vonage for over two years. I reviewed it after 3 months, and since then I'm still a happy customer.
I couldn't port my number because I was already signed up with a fleabag alternate carrier, so none of the portability issues came up. I've only had two times where I needed customer support, and one was resolved by email, the other by calling within 24 hours. Generally speaking the sound quality is good, but I have noticed some degradation on occasion, similiar to a dodgy cell phone call. It's hard to know if that was my service, though, since I am frequently talking to people on cell phones... But these instances are rare for me.
I consider myself the ideal Vonage customer in that I have good, reliable broadband, and use my phone very little. Thanks to Vonage, I've reduced my phone bill from $80 to $18 a month. I have no doubts that the customer service isn't ideal, but when I am paying bargai...