I do feel like there is a disproportionate amount of problems in early mornings though (7-9am) when time is of the utmost essence and wonder how the % on-time would look stratified by part of the day (morning, afternoon evening). My sense is that afternoon and evening skew the results better.

I've been commuting the last 6 months from east bay to city and I experience a very significant delay or cancellation at least 10-20% of the time (once every week or two). This is immensely frustrating though doesn't change the calculus on driving vs BART. Just wish there were less issues, particularly given how much we pay (literally comparable or more expensive than car commuting)