I love using the timelog categories! It helps us do a deeper dive into where our time is spent. This is when people remember to enter a category, of course. I find myself having to run a report and hound people to update their categories. Asking them to enter their time is already painful enough, now having to go back and say "Opps, you forgot to enter your category." adds another layer of annoyance.
It would be great if when the account admin choose the option to use timelog categories there is also an option to make it a required entry when someone hits submit for their time.