We had unlimited leave for dome senior employees for a while. Those employees ended up taking less leave than they did before and so we canned it.

We have generous leave allowances (18 working days at a starting level.) We also have a flexible sick leave policy - there is a fixed amount but we've extended that for individuals on occasion when the situation demanded it (long hospital stays etc.)

So in theory unlimited time off sounds good, but in practice its not a perk.