I stayed at three hotels on my last trip to Greece, they were all good but Kronos was the star.
It had a good air-conditioning, good wifi, a great shower with fantastic water pressure and a really good breakfast buffet (the yogurt is particularly good).
It's also located in a very beautiful and convenient part of town. There's really good restaurants and cafes just outside the hotel. The Venetian castle, historical centre and bus to Knossos are all less than 5 minutes away.
But the best part is the staff. They respond to emails promptly, are courteous, speak fluent English and were available to assist whenever asked asked. Kronos hotel is a true hidden gem amongst Heraklion hotels..