My wife and I use it. Here is my referal link if you decide to got that route.

We both get a $19 credit.
http://referrals.republicwireless.com/a/clk/1wx9l0I use WiFi about 90% of the time so it works great for me. An added benefit is that I can't get cell signal in my office, but now I can use my phone over my work WiFi. If you want something that works always with no nonsense, I would avoid it. If you don't mind a few quirks now and then and what to only spend $20ish a month for unlimited data, then go for it.
They are supposed to come out with new phones by the end of the summer/beginning of fall. I have the current phone Motorola Defy XT. It's based on Android 2.3, so it is old by today's standard. Also the phone has a small amount of on board memory which can limit the amount of apps you can use. It overheats when you charge and use GPS at the same time.
In the end, I am saving about $30 a month AND we have smartphones now. For me it is worth some of the quirks. If it were me, I might consider waiting to see what the new phones are or do the $29/mon plan until they come out. If you wan to more, let me know.