Well, I recently visited Crete. Funnily enough, I started a thread here on EN World for advice.
I can't speak about the rest of the country but Crete is really wonderful, though I visited in an off-peak time in May when it wasnt' overcrowded or unbearably hot.
There's a good mix of watersports, sightseeing, hiking, museums, etc, plus a relaxing atmosphere with lots of reasobably priced restaurants and cafes.