I think Acorn is a fantastic addition to Walnut street. We went for a birthday lunch in early March. The atmosphere was calming and the service was fantastic.
My friend's ordered the omelettes and really liked them. I ordered the grilled cheese, but didn't care for it-- all I could taste was thick, American cheese. I noticed this isn't on the menu anymore, so maybe they took it out of rotation. The side salad was simple and delicious.
This is definitely the place for a nice sit-down lunch. I'd be back to try some other things on the menu.