My wife and I use cricket (aio) and it gets the job done for us.
I pay $90 a month (10 dollars off for having 2 lines. I use the $60 5gig 4g/LTE data before throttle wifey is on wifi a lot so she's the cheaper 500mg fast data).
The iPhone app is really nice in terms of keeping track of data usage. I did bleed out all the data and sure enough it just went to a slow Edge 128/256k speed or whatever. The edge did still give me a solid iheartradio feed on the iPhone all day.
The 4G/LTE data is capped at 4mb-8mb but still fast enough for me to run netflix or youtube with only a minor annoying buffering signal to start it off. FaceTime, sms messaging visual voice mail all works on cellular data.
The new cricket uses At&T's towers which is solid in my location. I have no clue what all towers they have access to in terms of roaming/prepaid/postpaid but I do not travel much. We both use Verizon iPhone 5s as it comes unlocked for pretty much anything cdma or gsm sim card based.
I love the prepaid as each month if I want I can switch the plan or leave the carrier if I want to.
I have been with various post and prepaid plans in the last few years with an iPhone 4s now 5s and the aio/cricket is my favorite as the plan is inexpensive with reliable service in my area and most basic iPhone features you want to work does work.
Customer service I have never had to contact as I have not had any problems yet.