Sprint isn't going to let T-Mobile's iPhone upgrade promo go unanswered. It's launching iPhone Forever, a payment plan that lets you upgrade iPhones at any time without facing an up-front payment or a rate hike. So long as you're willing to shell out $22 per month on top of your service plan ($15 if you take advantage of a pre-2016 promo rate), you can upgrade to the newest iPhone on a whim. This theoretically saves you a ton of cash if you always have to own Apple's latest and greatest.
Whether or not it's a deal depends on what you're looking for both in the iPhone itself and your service. It's fine if you don't need more than the base iPhone, but that advantage disappears if you want a higher capacity or a larger screen. Also, the big savings over rival carriers hinge on heavy data usage. If you don't need unlimited (or effectively unlimited) data, the price gap is going to shrink considerably. Still, this is a good deal if you both have good coverage and don't plan to switch platforms -- and it's clear that Sprint's beef with T-Mobile is paying dividends for customers of both providers.
Photo by Will Lipman.