As for vacation, why not - you get 2 weeks vacation as a signing bonus, plus 3 weeks/year. This accrues up to X months. Seems to solve all of the problems. If you want to stick with the no vacation policy, assuming you're the founder, it means that you have to take long, extended vacations. If you want your employees to be comfortable taking two weeks off, you have to take two weeks off and make people know that you're taking two weeks off (and not work those two weeks, at least as far as people can tell). There are always deadlines, always important meetings, and I find it impossible to justify taking an arbitrary amount of time off with no guideline. The point of vacation time isn't trust, it's to set that guideline - I am here to work, but I need to know what the expectations are. You can deal with the outliers as they come up - if one of your good employees wants to take two months off in the summer, you guys'll work something out.
Then I think having no sick day policy ("come to work sick and you're fired") and a flexible work from home policy makes this less about beancounting and more about taking time off to energize. Everyone loses a few days a year to appointments, a cold, a sleepless night, etc., and hates having to take those out of their vacation days (or are forced to lie about being sick).