I have RW and it works fine for my needs. If you have similar needs, it may work for you.
I had Verizon but where we live the service is terribly spotty. I took most of my calls on the front porch, which is less than ideal. RW fixes that problem for me. I can take a call on my couch.
Other than that, RW has all the drawbacks mentioned in the other thread. I just don't happen to care about MMS and cell picture quality. The biggest reason it works for me is that I now have service in lots of places I didn't have service before because of the VoIP setup.
The main reason I went with RW is that my company pays be $40 per month in lieu of a BlackBerry, so I make a few bucks a month and get free cell service this way.
Hope this helps.