Was there a few years ago but loved it.
Quite a small island and the people are great & very friendly.
You can get the local bus all over the island so easy to get to all the other little villages. Only trouble was all the seats were highly polished so we were sliding from one side to the other as it went round the corners! Might have changed since we were there, though.
If you go down to the harbour at Kos town, you can get boats to some of the other little islands such as Kalymnos which is a lovely place, and don't miss the boat trip to Nisyros,called the volcanic island because it's just that. A deserted volcano and you can walk right into the old crater and across the sulphur beds. It's a bit stinky but quite an experience.