I just wish more companies communicated using iCalendar. In work calendar events are ubiquitous but I have found it really valuable to use them to organise my personal life as well. The problem is that it can be quite tedious to enter everything by hand. I wish cinemas, theatres, restaurants, hotels, airlines, train companies, etc etc, all sent you calendar appointments when you booked with them online. In my experience only a minority do and even the ones that do often don't do it right (eg, British Airways gets the timezone wrong).

I also sometimes wonder if we couldn't create a better calendar event format using JSON or something, but iCalendar is powerful enough for 99% of use cases - I just wish it was used more.