The Greek Festival doesn't change much from year to year. It's a well organized festival that includes Greek food served indoors in a large dining room or outside at booths behind one of the buildings (which is a little difficult to find). There are a lot of desserts outside but they are not covered so you have to be careful with those. We found the same desserts boxed up in a room inside next to the main dining hall so that was a little more convenient. They have some vendors inside and outside. Not all of the vendors are Greek-themed but that's okay. The basement of one of the buildings had historical lectures about the Orthodox Church and Greek culture. The church itself is beautiful and they have free lectures every hour.
This is a nice event but it is definitely the same thing every year. I believe I first went to it 10 years ago and the festival is exactly the same. The parking is tough especially during peak times. If you just want food, they have a drive thru on Winthrop Ave but note that during lunch time there were at least 15cars in line for it. If you haven't been to the Greek Festival, I'd say go. If you have been to it, it is the same festival, so I would not make it a necessity to return.