In early Sept, after having been with ATT for 9 years, I switched to Tmobile. My main reason was to save $. ATT - $262 (total) for 4 lines with 2 Next plans and 15 gb shared vs T-mobile - $187 (total) for 4 lines and 2 Jump!on Demand and 10gb/line ($120 for 4 lines). Plus, I can add several (4-7) more lines w/10gb per line for $20 per line. Also, I can double the data on any line for an additional $10. And, free music streaming (at least, no data usage). To really save, get some friends aboard and you can really max the savings and features.
What's really nice is that my coverage is better and my download speeds are more than doubled. At present, I haven't traveled so there might be a bit of a difference, then?
T-mobile is making the other carriers change their plans and that's good for all.