I'm not sure why traveling all over disqualifies people from "crappy service bashing." T-Mobile bills itself as a nationwide network, and even Sprint, problematic as they are, seem to offer at least some level of coverage nationwide.
T-Mobile repeatedly bashes AT&T and Verizon and tries to bill itself as a carrier worthy of switching to, and "breaking up" from your old carrier. Not "hey, T-Mobile is great if you stay in urban areas and don't travel... if you do travel or are out in the suburbs, then maybe you shouldn't switch."
If T-Mobile wants to play, they should at least perform half as well. Or, they should bill themselves honestly: a low-price carrier that COULD be better if its Chief Executive didn't prefer to talk trash on Twitter all day and half-heartedly seek buyouts on his network, rather than spend time and resources to fix his network so it could speak for itself. That way, instead of getting disappointed, people would know up front that they're going to have to sacrifice speed in the suburbs, and get no coverage in the sticks, in order to pay less.
That said: I DO have the T-Mobile free 250MB data plan (got it during the promotion) on my iPad Air. Do I like it? Sure, you can't beat free, and when you're not paying for your data, beggars can't be choosers. When you're in a good coverage area, the LTE speeds are decent if you're paying for them, obviously phenomenal if you're not. And I've even paid for the monthly data pass a couple times, both to support T-Mobile and to keep using fast data on them past my 250MB. And I feel I mostly got my money's worth when I pay.
But it's also shown me the limitations of T-Mobile. It's okay for casual use in heavily populated areas, but that's it. Definitely not a carrier I would switch to for my iPhone (even though I once wanted to), or go on a regular plan for on my iPad. There's just way too many holes, and they still rely way too much in Edge in a lot of areas.