The correct name for this pho shop is Pho Gia Truyen. There is also another listing in TripAdvisor called Pho Bat Dan but it is the same shop. When a Hanoian talks about Pho in the old quarter, it is by default this one.
What you have read in the postings are correct. Let me elaborate a little more……..
My friend and I read about pho Gia, and wanted one last bowl before leaving hanoi and it was the perfect decision. There was a line out the door, everyone except us was vietnamese, and the pho was absolutely delicious - so fragrant and tasty. Thanks for leading us there trip advisor!