I own my own company now, but I've worked at both companies with unlimited vacation and those with a set number of days. Allowing unlimited vacation but tracking sick days seems strange - how do you define the difference, and why do they care?

I've also found that once you're in a system, change makes it worse even if it's too a better system. If you go from unlimited to a set amount, you feel like someone has now capped your time and is watching you (even if the cap is so high you would never hit it). If you had a set number of days and they switch to unlimited, you feel like now you don't have a guaranteed amount of vacation. The loss aversion is really strong.