We always read the "terrible" and "poor" reviews first, because it seems that there can be an inflation of "excellent" reviews. For Nha Hang Yen, I have to disagree completely with the critics. First up, the service was impeccable. Seeing as it is a popular restaurant, we arrived when it was full and the staff still went out of their way to accomodate us when we returned a while later. Staff spoke good English and were very friendly. The interior is possibly the best in Vietnam so far, fans, lovely colors and flowers on every table. Everything was clean, even the toilet held high standard.
Food was very good, tasteful presentation and wonderful flavors. We overheard the couple seated next to us complaining about small servings, which is just outlandish and rude. Pricing provides good value, and the size of the servings are reasonable, we, two people, dined for 250+ VND and were well satisfied. Someone wrote a review and called it "non-vietnamese food". Totally disagree, this was reminiscent of authentic Vietnamese food served to us at non-English menu food stalls in HCMC and truck stop restaurants along highways.
To sum it up, it is fair to be wary against anything offered in the "tourist district", but Nha Hang Yen transcends the hustle and bustle and provides a wonderful experience.