Green Leaf certainly seems to be the new Seattle chowhound darling by the messages here and on "those other message boards" but I went there for lunch yesterday and was not especially impressed.
My coworkers got the duck noodle soup, and while the duck was very tasty, the broth was thin and "missing something". My wife got pho tai with overcooked noodles in a broth that tasted "woody" (her word, but it's about right) - this was the biggest disappointment. It was nowhere near in the same league as Pho Bac or Pho Cyclo. They didn't even have their own sambal to help out the broth (and it needed help), but just plonked down bottles of Tuong ot Sriracha and lee kum kee hoisin.
The two bright spots were the bahn xeo and bo cuon la lot. I like the bahn xeo at Pho Bac well enough, but you could actually taste the coconut milk in this version, and one order was big enough to feed 2 normal people for lunch.
The beef la lot at Green Leef was, honestly, the best I've had. Maybe Tamarind Tree gets to the same level of flavor, but they're always so busy that they haven't ever arrived at our table hot.
The verdict after lunch was that we'd all be willing to return to try other dishes on the strength of the ones that we really liked, but that it won't be replacing Pho Bac as our usual Viet lunch spot in the ID.