I'm a Wizards full STH so I'll be getting plenty of practice before the Nats return - doesn't really sound all that involved though.
The real risk, though, is of the card getting degaussed due to being placed in one's wallet next to a credit card or other magnetised medium - I'll probably still use my ticket carriers to prevent this.
I just hope the entering queues don't become like SmarTrip queues on Metrorail/bus....
I'm actually a little worried about bottlenecks at the entries under this system. It says they will print you out a "seat locator tab" when you come in, which they frame as being to tell you where your seat is, but of course is really so the usher has something to check to make sure people are in the right section. That seems like a potential mess, because now instead of just swiping a ticket and walking in, people going in using a card will need to have the ticket taker print them out something to show the usher. It's hard to imagine that not slowing down the entry process.