I'll jump in and vouch for Ting. Ting is fantastic as long as you adjust your usage to operate mostly on wifi, which hopefully is no big deal. I set my wife up on Ting a few months ago and the bill is consistently about $20. Woo!
As for your conversion from Verizon, just do the math. If you want to stick with Apple, consider selling your iphones on ebay and buying used/unlocked iphones on ebay as well. The iphone 4 we bought was $220. Even if you don't sell your used phones at all consider this.
$440 for 2 phones, estimated bill $60/m compared to current $144/m, I show you break even in 6 months. After that it's just sweet sweet savings.
For others who may be reading that are under contract, do the math, it may be worth it to break the contract over the long run.
Alternatives, Republic Wireless get's a lot of attention around here, but no iphones only Android I think. Airvoice had some attention for a while, but not so much lately. I used Airvoice for a year or so, and you can't beat $10 a month for a dumb phone...