If you've ever been to Gab and Eat in Carnegie, the interior and atmosphere at Frank and Shirley's is similar. The food isn't quite as good or filling though.
When we got there around 10:30 on a Sunday morning there was only one open table and they seemed pretty busy. But they keep the line moving incredibly quickly. We were seated, drinks delivered and order taken with five minutes. Our food came five minutes later, and we were out the door in about 20 minutes total. I ordered a ham and cheese omelet and my wife ordered poached eggs, extra hard. The omelet was OK; nothing special. It was actually on the small side and instead of freshly cut ham off the bone it was prepackaged ham cubes. My wife's eggs came out very runny, aka the opposite of how she asked for them.
I gave it three stars though because while it wasn't the best, the eggs still had flavor and the whole process was very quick and efficient. But sometimes, at least at breakfast, we kind of like waiting and relaxing.