I bought one about a month ago. It works pretty well. I would only use it when your battery is low, otherwise it's wasting battery and you won't have any when you actually need it.
I used to have an iPhone 6 and iPhone SE. Paid both of them off and just recently bought a iPhone 7 256gb. Honestly I feel like the water/dust resistant alone is a great reason to upgrade. You won't have to worry about getting your phone wet if you "accidentally" jump in the pool with the phone...
Verizon is good for people who live in rural areas, lol like me. If you live in a major city like Boston or LA, then yeah T-Mobile would be amazing. I've tried to use T-Mobile in my city and I get like 1 dot. That's both on a SE and a 6.
Switched from my iPhone 6 to an iPhone SE. Gotta admit , when I was purchasing a phone 2 years ago I should've went with my gut and got the iPhone 5S but they didn't have the color/capacity I wanted; so I settled for the iPhone 6.