I do not have any experience with Odyssey sailing. I am actually a "competitor" of Odyssey sailing, but I can share with you a few things I know about them:
It is a yacht charter company in Greece located in Volos city and operating their yachts mostly in the sailing area of the Sporades islands (i.e.skiathos, skopelos etc). It happened that they asked me for available yachts in other areas in Greece, so we have exchanged a few emails between us. They seem to know the business and most important to care a lot about their clientele. I understand they will do the best possible for their clients.
Generally speaking the sailing yachts for charter in Greece (4-5 years old or younger) are well kept.