We took the Split Vision Sightseeing tour which lasted about 1 1/2 hours. Afterwards we visited the markets and stayed pretty close to the port. Since this was the first stop, the cruise was still new and we didn't know what we really wanted to do. I would advise to do your research and have an idea of what yo want to see/do when you get there...it will save a lot of mindless wandering!
Ephesus was nice. Again, beware of the tourist traps. These are professionals and know how to make their money. You will get off the ship thinking "oh these people are so friendly" but no, all they want is your money! If you show any amount of weakness, be prepared to be taken! There are several nice items there and a ton of shopping, but know what you want, know what you are willing to pay, and stick to your guns. They want a sell so if you walk away they will continue to bargain...even to the point of being rude at times.
Santorini was great! The donkey experience was one quite like no other and one I won't ever forget! Again, Santorini is a huge tourist attraction so you will either pay the tourist price or you will pay the local price. They are not willing to bargain/haggle either. We bought the traditional Greek cardigan that you can style 50 different ways and we paid over 50 euro in one store and only 28 euro in another store. Same quality and same material...only difference was the tag on the inside. We opted to use the bus to get around the island and towards the afternoon/evening it was way off schedule. We ended up taking a taxi to avoid missing the return time to the ship. All in all Santorini is on my "return" list but not on a cruise...not enough time to really enjoy the island.
Olympia was great to visit and is amazing how well kept the ruins are! We took a local bus to Olympia, enjoyed the sights, then came back to the port 2 hours later. From there we rented an ATV and went to explore. Enjoyed some of the local fare and chatted with some of the local store owners. This was probably one of the most laid back ports and the people were genuinely friendly. They weren't pushy and always trying to sell something, so it gave us a chance to truly talk and learn more about the culture.