I went from Verizon to Tmobile and have mixed feeling about the switch. The price is MUCH better, saving almost 100 dollars a month for our 3 phones. The coverage is not even close as far as traveling goes. We are in Dallas, but have taken our phones on a few long road trips both south, north and west and it seems to be the same story anytime your on a highway between cities...its a bit of a exaggeration maybe... but it feels like anytime I am not within a few miles of a major metropolitan area I have either voice only or nothing. The non city coverage is basically non existent. This was with our nexus 4's which were not LTE compatible, I just got a G3 so I am hoping possibly that adding the LTE in will help with coverage, but I guess we will see.
With verizon, I can't remember a time I didn't have a signal, even in rural Illinois while visiting family.
Customer service has been good with both companies, but I really prefer the changes Tmobile is making with its uncarrier stuff, which is the main reason I like giving them my support and money.
But like I said, if you travel a lot as you said, then coverage should be a concern.