My wife and son are flying MDW-MCO tomorrow at 7:30 for Star Wars Celebration V. I have been curious about whether iPhone check-in (running with Wifi connection) is comparable in speed to doing it via regular wired computer. So I pre-entered their 2 PNRs, one on each device, and within 5-10 seconds of T-24 hours, attempted to check-in both simultaneously.

The wired computer yielded A37, and the iPhone was A38.

So unless this is going to be a really empty plane and I had no competition, I guess iPhone check-in is quite good.