I was in Greece last July. I was a little concerned to go due to the unrest and economic problems. It was a fantastic experience and I'm very happy I went. You really need to go. I don't know what your interests would be, but I did a tour of Classic Greece. I saw most of the sites that are relevant to Greek history. I was only able to visit a few islands ( I could only get two weeks off from work). The islands are so beautiful and I do really regret not having a few more days to cruise.
It is really sad though to witness the poverty and struggles. Athens shows the most signs of the difficulty. The islands and other small towns are much more idyllic and preserved. Oh, and the food is incredible