I think it depends entirely on the leadership team and company culture. I work for a company with unlimited PTO and it works well. They encourage people to take it and managers keep an eye on it to make sure you are taking it. Everyone I've worked with takes time without really worrying about it. Some people have even taken sabbaticals for 2-3 months (you have to be around a bit before you do that). Having said that, it does seem ripe for abuse with the wrong company. Also, I would rather take time than bank it for a payout.