T-Mobile's standpoint, it was a success because lots of people used the app. On the side of the users, however, a different story is told; especially with the fine print on the deals.
When T-Mobile announced that they were giving away free pizza from Dominos, it excited a lot of people. Unfortunately, what they meant was that the freebie was only limited to 100 pizzas per store. And in areas where there are a lot of T-Mo users, the limit was quickly reached. This became a problem because several didn't notice the fine print. They thought that Dominos was not taking their coupons.
Apart from the fine print, it was quite unfair of T-Mobile to tie up the deal with phone numbers. With what happened yesterday, there were some users under a family plan who were able to get 5 free pizzas. Sadly, this led to some users who were unable to enjoy their free pizza.
While these things are "pretty petty" for T-Mo subscribers to complain about (they're free after all), it still can be disappointing for users to expect that they were getting something for free and end up with nothing; especially those who've been waiting for a week. Hopefully, this experience will prompt T-Mo to be more cautious about how they're giving away the freebies under the T-Mobile Tuesdays app. At the same time, this will also encourage users to read the fine print whenever they're interested in a freebie from the app.
Update 6/15/16 5:30 PM:
John Legere announced that they will no longer be giving away free pizza because Dominos could not keep up. The T-Mo CEO promises they still have freebies from their other partners they coordinating with. More on this as soon as they officially announce it.
Source: PhoneArena5/ So much demand from our amazing customers for @dominos pizzas, they can’t keep up & we can’t thank you w/pizza next week.— John Legere (@JohnLegere) June 15, 2016