I have my wife on Republic through UltArc's referral and she is very happy with the $25/mo unlimited phone/text/3G. She has been using the Moto X for over a year and sees no reason to replace it.
That said, I just bought an LG Volt for Mom and Dad for $30 each, and have them signed up with
Ringplus. The Bella plan is $10/mo for each device and provides 400 minutes, 400 text, and 300MB data. The catch is that you listen to ads instead of hearing the normal phone ring when you place a call.
I'd go with Ringplus myself if I didn't have my ridiculously expensive iPhone/ATT provided by work. It's hard to beat a $30 smart phone and $10/mo plan.