I went to Greece a couple summers ago and overall, I had a great time. I would recommend not staying in Athens very long, as I found it to be overcrowded, terribly hot (at least in summertime, which was when I was there), and very polluted. I felt much better and could breathe much more easily once I got out into the countryside. :) I'm not sure if you are planning on doing much visiting to historical sites, but that's mostly what I did, so if you want specific recommendations on sites to visit, I would be happy to offer some.