Originally, Touch ID was supposed to improve its accuracy every time you scanned a particular finger. But that was not true if your initial set-up was a bad one. If the first scan you took had problems, your scans would not gradually improve, unless you set-up your finger again from scratch.
With iOS 7.1.1, a poor set-up the first time you scan your finger, won't lead to constantly poor readings. In addition, the update improves accuracy using Touch ID. The update to iOS 7.1.1. also lowers the number of calculations required by the Apple iPhone 5s, before it unlocks the phone. Bottom line? A faster and more accurate fingerprint scanner on the device.
With iOS 7.1.1 Apple now takes multiple scans of each position you place finger at setup instead of a single one and uses algorithms to predict potential errors that could arise in the future. Touch ID was supposed to gradually improve accuracy with every scan but the problem was if you didn't scan well on setup it would ruin your experience until you re-setup your finger. iOS 7.1.1 not only removes that problem and increases accuracy but also greatly reduces the calculations your iPhone 5S had to make while unlocking the device which means you should get a much faster unlock time.-Apple iOS Security White Paper
And code found in iOS 7.1.1, reveals that Touch ID is coming to the Apple iPad Air 2 and/or the next iteration of the Apple iPad mini with Retina display. The faster and more accurate the fingerprint reader works, the less "gimmicky" and more use useful the feature appears to be.