I've eaten at Six Penn for dinner and enjoyed it very much. I wanted to get dinner reservations for after a show at Heinz Hall today, but they were booked when I tried a week ago. So, I decided to have lunch/brunch here instead. Know that even with reservations you may end up sitting I the second level, where you have "full service," but it means the bartender will run about for you and everyone else in the area. 12:45 on a Sunday is post brunch and you have a small amount of menu options. My lemon creme waffles were cold and one was slightly burnt. You will still be hungry afterwards. You self seat and need to wait to have the table cleaned as well.
I am amending this the day after my review because I got an email that I was a no show for my reservation. I did in fact tell the desk I had a reservation and my name. Food disappointing, service disappointing.