I like that it's easy to create ads, set up filters so you can find specific skills or experience in your area of expertise/experience as well has quick turnaround times if there are any changes needed after initial posting (which happens pretty often).
Honestly though - not much! It works great but honestly this isn't something we've had an issue with since starting using unicorn hunt over 3 years ago now.. Just be patient when creating new adverts etc because they do get updated frequently which makes sense given how fast things change within our industry / market trends & such.