I love playing with other people's phones, especially if they're iPhones. Also, every time I pass an Apple store/retailer, I stop and play with the devices in there. I don't actually have an iPhone, hence why I have what my friends tell me is a creepy obsession with them.
They all worked perfectly except for two I have tried, both which really shocked me. One because it was just a few months old and refused to work at all, and the other because it was a display at an Apple store. But I have tried Touch ID on many, many phones and I'm very impressed with it.
Also, through my fleeting experiences with all those iPhones, I found a neat trick though that allows you to save two fingerprints in just one slot. You do the normal setup but you alternate two of your fingers. I don't know if this will deteriorate faster, but all the times I had tried it, it quickly recognised both without error. It worked with up to four fingers for me.