...Joining this thread simply because i grew up in California spoiled by great Vietnamese food within five minute's drive from any possible given location, and I'd love to know about good Vietnamese food out here in HK.
The only Viet restaurant I've been to so far that I found acceptable enough to go back to when I simply need my fix (not saying it's authentic at all, but I thought it was decent enough to get the job done in desperation, for me at least) is Nha Trang Vietnamese Restaurant on Queens Road East in Wan Chai. It's on the second floor outside to the left of the Hopewell Center, next to Cafe de Coral. Have tried the Bun Bo Hue as well as the standard Pho (no "dac biet/bo vien" super tripe/meatball combo available, but they have brisket/slices) and one of the cold pork chop Com dishes there so far. None were outstanding, but all were acceptable, which is honestly way better than I'd expect to find here in HK.
I just checked, and the English reviews on Openrice are all pretty terrible, but I'd give it a shot if you're as desperate to fulfill that Viet food craving as I've been. Let me know what you think, and please keep the information flowing. You guys all sound like you appreciate good Vietnamese food, and I'm 100% open to trying your recommendations.