I'm with you guys. Andrew Scott did a phenominal job, but the plot and story were subpar. This was not "Black Mirror." Black Mirror is at its best when it has a Twilight Zone feel with twists and you end the episode contemplating what you just saw. The plot was clear early on, so there were no twists or surprises and I certainly didn't spend time thinking about it afterwards.
I mean, in summary, a dude looked at a notification and got into a car accident, killing his fiancee. He blamed himself and wanted the owner of the software to know. In the end, he was killed due to his actions.