I've eaten a lot of Vietnamese food around the US, especially in the major Vietnamese hub of the Twin Cities. As such, I know what I'm talking about.
Pot-Au-Pho surprised me with some unusual dishes. The first time I went I had a "roti" dish with curried tofu. It seemed more like a Malaysian-Indian hybrid dish but was excellently prepared: a flaky, crispy piece of roti with well-spiced, flavorful tofu in a curry-vegetable base. Really impressive, unusual stuff.
The second time I went I got some bun chay (noodle stir-fry) with vegetables and tofu. A friend of mine had ordered this dish the first time around and it looked spectacular; when I got it weeks later, it was limp and bland. I'm not sure what changed (maybe it was a different cook?).
The service is decent. While the top floor is cramped and messy, I think you're expected to eat in their dimly-lit (but sort of romantic) lower level, which is far cleaner and nicer.
I had the same waiter both times and didn't bat an eye when I asked if my dishes were vegan.
I look forward to checking out Pot-Au-Pho to see if they can keep up their quality. Maybe the second time I went was an off-day.