The ability to see who's been in an interview or not since last week! And then being able to follow up with them if they didn't show - it makes my life so much easier as I know where things stand at all times!! It does take some time getting used too but once its there we've never looked back again (you can set reminders also!).
We have only had good experiences using snaphunts services. They are very helpful and quick responses from their team when needed. Sometimes emails don't go through straight away which causes us issues sometimes though this hasn't happened recently due to improvements made by our recruitment manager regarding email addresses etc.