I bought a used sprint evo 4g from ebay and hooked it up on freedompop's free service. 500 MB data and 200 minutes voice per month. $0. Voice quality sucks over 3g (its VOIP voice over data) and I can't get the 4g to work. I rarely use voice so it's not a big issue. Data works well. I'm on wifi most of the time, and voice is good over wifi.
I tried the evo 4g GPS last week for a trip to/from the beach and it crashed and rebooted the phone every 20 minutes. I'll probably flip the phone on ebay and get a better phone for freedompop so I can use the GPS without it rebooting on me.
We have DW's $10/yr plan on T-mobile for voice if we need it in an emergency while traveling.
Retired in 2013 at age 33. Keeping busy reading, blogging, relaxing, gaming, and enjoying the outdoors with my wife and 3 kids (4, 10, and 11).