I went to that McDonalds about 3 months after it opened, it was a well planned family outings. It still is one of my favorite stories that I tell. The line was about an hour long. Once you got within 15 minutes of the doors, there were helpers who helped people who have never been with explanations of what to expect and how to order, and helped one plan an order. I got in and ordered a hamburger and Coke, and I remember being right next to a tall black guy which was still quite exotic there who was also ordering something. Our orders must have gotten crossed because I got cheesburger and clear Coke, which I was really surprised about and I now know was Sprite (and I actually like it more than Coke because of that first taste, even though I don't drink any). The meal was served with real metal cutlery and there were even plates involved that you could put your meal on, and was quite good. The government's allowing McDonalds to open was apparently stipulated on them sourcing their food locally, so the meat was actually meat, and tomatoes on the cheeseburger actually were tasting like something. We took the box that the hamburgers came from home to reuse, it was a sturdy paper box, but the cutlery you had to return. Definitely the best tasting McDonalds meal I ever had. The USA experience when I landed here in 1995 was just completely from another planet.
I (an American teen) also ate there in April 1990, with partially overlapping observations. The food was higher quality than anything else I ate during a week in Moscow, but it struck me as pretty standard McDonald's fare. As for the line, it was very long, but moved in fast spurts. Customers were admitted in waves and it was the most efficient retail orchestration I'd ever seen. There was some magical blend of Soviet queuing efficiency and fast food efficiency going on that left a deep impression.