Zorba's is another place that my parents remember from their time as graduate students in the late 70's, and it appears to be somewhat of an institution now in Champaign. I went with my parents on a summer Tuesday right at opening time and our food came out quickly. It's cafeteria-style seating and the place filled up within a half hour.
We got 2 of the beef/lamb gyros and a Greek salad. I thought the gyro was okay. I mean, totally acceptable, but honestly I've had better at the Greek-fest thrown by the little Greek Orthodox church across the street from me in Boston. The one I'm used to has a lot more of the meat, better sauce, and way more tomatoes and more thinly-sliced red onions (instead of the white onions used at Zorba's). The fries that came with the combination platter were not good at all. Those were mostly left untouched.
Overall, Zorba's delivers reasonably good value, and was a quick, convenient lunch stop in Champaign. I didn't think the food was great by any means, but it gets the job done.