Typing Patterns for Authentication
A couple years back, I was part of a project which implemented this product with little success. Your second point is right on, if the user switches keyboards (laptop vs. PC vs. home PC), then the system doesn't recognize their pattern and they need to re-register, which is a time-consuming process. Furthermore, the authentication is highly sensitive to latency, which results in the same failure to authenticate and subsequent need to re-register your typing cadence. Another point to consider is that it is highly sensitive to minor changes, such as if the user has a bandaid on one of their fingers then they experience the same issue.
To be fair, the sensitivty settings are configurable.
Needless to say, the user communtiy revolted, and we pulled it.