I have been lucky enough to be there a few times and there is always something that amazes me and surprises me, a beach, a view, a sunset, a restaurant...
I had the chance of staying at Perissa Beach this time, where the "black" beaches are. Everyone is friendly and the are restaurants for everyone. Fira is a great place to party (big nightclubs). The sunset cruise is amazing, the food is OK, nothing spectacular (the cruise is 35€ with dinner included and transportation from different parts of the island to Athinios Port.
Do not miss the "white beaches" and "red beach". To rent a jeep or a scooter is fun, just be careful, they drive differently then us ;)