I've been with Sprint since 1998. Generally abysmal customer service, but if things work (and they generally do these days), you really don't interface with customer service very much. And in return, you do get truly unlimited data.

Sprint's biggest issue for 2014 is the too-slow rollout of 4G LTE to take advantage of all that unlimited data.

I could switch to Verizon and get exceptional coverage and better customer service, but I'd probably pay $100 more a month for the data.