I've been traveling a lot this summer, and I saw bad requirements exposed while waiting for my turn at the kiosk. If you buy an e-ticket, you can walk up to a computer, called a kiosk, insert a major credit card, and check in. No one calls you. You have to know the computer is called a kiosk (which is not the same as a mall kiosk). You have to know that you're limited to 2 bags, that you need an id (ok, I'm not sure how people missed this), and a whole bunch of other stuff. Lots of people travel in the summer who fly once every few months or every few years. They don't know what they're supposed to do.
While I was in line, the first people were happily waiting to be called to the people behind the counter. The people behind the counter were talking, waiting for people to come to the kiosks. I was too far away to be helpful — even I don't think it's helpful to yell across 20-30 feet, “Go use a machine!” Even if I'd yelled it, the people would not have known what to do. Finally, someone had pity on all of us in line, and explained that the people in line had to walk up to a machine.
Even when these folks moved to a machine, they didn't look at the machine to see the terse instructions — instructions you can understand if you've use a kiosk before, but not if you haven't. (Kiosks started about 6-9 months ago? and when the airlines started using them, they had helpful people standing around explaining how to use them.) These folks still thought they were going to be waited on — like the last time they flew.
I think the kiosks are too hard to use for a new traveler — they automate what a counter person does, not what a traveler does — but once you've used one, the rest are similar. But, here's a perfect example of not thinking about the consequences of changing how travelers check in. Sure, the airlines had plenty of helpful people when they introduced the kiosks, but they don't now. E-tickets don't say how to use the machines. You already have to know how these things work to use them successfully. I'm allowing more time at the airport these days, to accomodate the people who just don't know. (And to accomodate the people who refuse to take off their shoes in the security line.)
What have you changed in your product? If you have non-frequent users, do they know what to do? Do your users know how to use your product — especially now that it's changed? Make it a conscious decision to change things, and then decide how you'll educate your users.