I worked for a Denver-based SaaS startup with unlimited vacation. I never felt that it hindered anyone, and most employees only took off the usual 2–3 weeks. It was really nice if you got sick, as there wasn’t any pressure about staying home and getting healthy.
In contrast though, the CEO was a big stickler about everyone being in the office, not working remotely, and being “visible” until 5:00 pm every day. I always thought that contradicted the self-managed vacation policy.