Just wanted to share this. I took MMM recommendation to try Republic Wireless. Tried it for about a week and the only complaint I had was that my area has super terrible Sprint coverage, so I was going to have to offload most of my calls and text onto wifi anyway. So, I sent the phone back and got my money back (and they were awesome about it...I would wholeheartedly recommend Republic Wireless to anybody who DOES have decent sprint coverage in their area).
Instead, I went back to my ole Galaxy S3. But instead of paying for a $100 per month full throttle plan, I decided to sign up for Google Voice, got a free number, and axed my plan entirely. Found an app in google store (Talkatone app) that allows me to use google voice on my phone just like a regular talk and text app and I have essentially free, awesome smart phone service.
But since I did not want to handcuff myself to wifi (the places where I spend most of my time have wifi, but I wanted to be able to use my phone anywhere), I signed up for a mobile hotspot. You can get them as low as $25 per month for 2 gigs, but I got the 5 gig plan for $50 through AT&T (because that was the lowest they would allow me to go). Sliced my phone bill in half, but I still have my full horsepower smartphone for well under half the cost.
I wrote a full article about it on my website (link is in my sig if you are interested). But I'm pretty pleased with it. Google Voice works ok. It has its glitches, but I'll take those glitches for the money I save.