Under this offer, T-Mobile customers who switch to AT&T can get $200 in bill credits on or before their third monthly bill, in addition to trade-in credit on an existing phone of up to $250. The trade-in credit is actually available on phones from any carrier and can be significantly less than $250, depending on the device.
If you have a fairly new phone and a case of buyer's remorse, this could present an attractive option. However, you can't trade one contract for another since the trade-in credit isn't available for phones already discounted in return for a two-year contract. This means your trade-in can conceivably get you a phone at near contract price without a contract.
In addition, the $200 bill credit may lessen the pain if you're looking to get out from under a T-Mobile agreement and facing a $100 to $200 early termination fee to get out of it, or if you'll owe hundreds of dollars for the phone if you leave T-Mobile.
John Legere, CEO of T-Mobile USA, responded to the offer with a brief statement, saying "This is a desperate move by AT&T on the heels of what must have been a terrible Q4 and holiday for them. I'm flattered that we have made them so uncomfortable!"
While T-Mobile's monthly plans cost a bit less than AT&T's, T-Mobile has been slow to roll out 4G LTE service and consistently ranks below AT&T's service in surveys and tests such as those performed by Root Metrics.
Also, AT&T has invested heavily in free Wi-Fi hotspots around the country in restaurants and shopping centers and makes it easy for their mobile devices to auto-connect when they find an AT&T hotspot. This can help conserve your monthly mobile data allotment.