The ease with which I can get audio from all over my office, into one station to be played everywhere without additional hardware or software; it's really that easy! When you have more than 4 people talking at once, things slow down considerably because each person has their own microphone - this makes scheduling difficult as well since there are so many different parties involved.
We use it mainly during interviews where we need multiple sources speaking simultaneously (for example, if an applicant was taking time off between jobs). It also helps us determine who may not want certain positions by simply having them speak about themselves briefly while candidates talk longer periods about what they're looking forward to doing upon hiring.