We went to Scala last year and are repeating the trip this year so as you can see we enjoyed it. We didn't do Ithaca last year but plan to this year. My advice is to shop around for a trip. Don't automatically book with your tour operator there are trips with local agents/operators that may be cheaper.Alternatively if you hire a car you may be able to take on the ferry to Ithaca from Sami but check with the car hire operator first!
I would advise you to also take the trip to Olympia on the mainland. This again will be an organised excursion and again I would say shop around. Check when booking that you will get a guide at olympia as it will make more sense to you. Check out the town restaurants in Olympia for lunch. Do not necessarily use the one "advised" by your coach guide as it may not be the best value.
Finally hire a car and dare to get out and about - (stick to tarmac roads) its well worth it.
P.S. This rating applies to my previous comments! Sorry!!