I spent most of January 2019 in Hanoi, there were other places near by I wanted to visit like Halong Bay and Hoi An but I was just working too much to take any side-trips. Overall the biggest impression I got is that the people are so nice and seem genuinely happy there. The food is great and ridiculously cheap and there’s a nice cafe and beer culture. If I came back again I would definitely rent a scooter since traffic is dominated by them; scooters driving on sidewalks, parked on sidewalks, things get pretty intense around rush hour.
I found it interesting that a lot of people are part-time vegetarians due to religion. On full moon days, or “moon days” you’ll find a lot more restaurants offer vegan buffets and specials. It’s worth paying attention to the lunar calendar if you want to catch some of the best vegan food, some places are actually only open on moon days.