Perivola, in the center of the island, has fresh water springs and the island's few remaining oak trees. The tiny village of Pano Kambos is pretty. In nearby Hellinika you can see mysterous monoliths.
The night life part of Ios is self explanatory and everywhere you look. But in town the favorites are The Dubliner, Sweet Irish Dream, and Slammer. In Milopotas is the Cyclades largest disco, the Scorpion. For a quieter time and nice sunsets the Ios Club on the path up to town is pleasant and more cerebral.
For dining, in Ormos try Psarades for fish and in Koumbara try Polydoros for traditional cuisine such as tzatziki, taramosalta, fish soups, fresh seafood and even vegetarian specialties.
In Ios Town or Hora the Lord Byron remains a favorite for traditional Greek food and rebetiko music. Near the Church is Pithari, one of the best restaurants on the island and with its own barrel wine.