My job involves a lot of deep work. Often I'll be so locked into the task I'm working on that hours will go by without me checking my mail or calendar. I also have multiple screens, and the web-based cal apps and the Apple cal app all only show notifications in the top right corner of the screen. These notifications are remarkably easy for me to miss, and therefore they make it too easy for me to miss the start of an imminent meeting, which I was previously doing often. Not a great look for me.
Busy Cal's pop-up meeting alert panel saves me. I set it to pop up and remain on top of all my other windows until I dismiss it, and to pop up both in advance of and right as a meeting starts, so that I'm prepared for the upcoming meeting too. I never fail to notice it - so finally I'm no longer showing up late for meetings on account of not failing to notice my meeting alerts.