The phone's motion tracker does a nice job of tracking your steps (it recorded about 8,400 steps when my Microsoft Band tracked 8,200 for the day) and automatically keeps track of how far you bike and drive, too. The glance screen now offers numerous options, and you now have control over app permissions — what apps get access to specific phone functions. Unfortunately, the Lumia 640 lacks the "Hey Cortana!" active listening feature available on the Lumia 930.
The Lumia 830 is arguably a better phone...but
Aside from the caveats I've listed above — especially the limited storage — I see nothing truly wrong with the Lumia 640. I just think that you'll be happier with the Lumia 830.
Right now, however, Cricket's offer for the Lumia 640 is also dramatically cheaper: By my math, it works out to $1,210 for two years of 5GB/month service, including the $129.99 up-front phone cost, plus taxes and fees. Two years of AT&T Next 24, plus the price of the Lumia 830, will cost you $3,080.16. (AT&T and T-Mobile have announced that they'll carry the Lumia 640, but as of this review have yet to announce pricing.)
By that metric, you may find yourself quite willing to put up with any quirks that the Lumia 640 offers. I will argue stridently that you'll enjoy the Lumia 830 more. But in the midrange phone space, price can be a major sticking point. In that regard, Microsoft's staunchly midrange Lumia 640 may be the right phone for you.
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