Using disposable swipe cards on New York's MTA can be frustrating. If the card gets bent, it will not work ever (this has happened to me and getting an attendant to help you retrieve the amount on the card is time consuming).
If you don't have a unlimited monthly pass, remembering how much money is still on the card is a small but present effort. Also, if traveling on a bus I often put the card in the wrong way first as there are 4 possible positions (because the magnetic stripe is only on one length of one side). Further, even if the card is put into the swipe section of the terminal correctly the terminal often will not accept the first swipe action. Rather it will digitally spell out to swipe again. I see this happen to others frequently.
I don't doubt that an extensive allocation of time and money has gone into the research and development of the disposable swipe card method. And its worth acknowledging the acclaimed design of the pay kiosks that dispense the cards; but I have a hard time understanding why reusable light metal tokens were not chosen. They can be inserted in to a slot with out fail ie. optimal entry efficiency, they last and can be reused infinitely, and they are easy to count out/ keep track of how many one has left.
Of course for unlimited Monthly passes, or unlimited week and day passes cards make the most sense but for infrequent riders I would advocate for tokens. You'll never see them scattered like garbage in subway entrances and on the tracks.
