It depends on your lifestyle, pretty much.
In this answer, I will mostly focus on HCMC, since I’m living there.
Weather
The Northern section has the lowest temperature in the country: ranging somewhere around 5 degrees Celcius during winter, and reaching approximately up to 40 degrees Celcius during summer times. The Middle section has a temperature of 20–40 degrees Celcius. Powerful hurricanes would usually hit the MIddle the most, then the Nothern. The Southern section is known for being sunny every month of the year, having a temperature from 25–38 degrees Celcius.
Food and drinks
The big cities in Vietnam are a paradise for those who like to eat and drink: dishes and cuisines ranging from Vietnamese to European and American; from cappuccino to boba tea. Cafes and restaurants rise like grass in HCMC: Tous Les Jours, Gongcha, The Coffee House, etc; while in Hanoi is less attractive in this side, but you still have sidewalk-restaurants serving ice tea in December.
A street in HCMC filled with cafes and boba shops, taken from https://vitenambiz.vn
Festivals
There’re also several festivals during the year. Lunar New Year and Christmas are the most “active” ones. Streets are decorated with lanterns/colorful Christmas decorations. If you want to experience the feeling driving through the wide streets with little to no traffic, then come to HCMC or Hanoi during the Lunar one. Shores and malls also have discounting programs during Christmas too. It’d be a nice time to chill with your friends and go shopping, while also enjoying the festive atmosphere.
Nguyen Hue Street during Lunar New Year, taken from Báo Dân Sinh, tin tức 24h tin mới nhất của báo dân sinh.
The Notre Dame in HCMC during Christmas, taken from https://www.baoxaydung.com.vn
An extremely deserted street leading to Saigon during Lunar New Year. Just wonderful, isn’t it? Also taken from Infonet.vn
Putting these aside, Vietnam has itself several issues worth mentioning too.
Food safety
Yes, many cafes and restaurants may unintentionally serve food or drinks that can harm people’s health. If you’re not too unlucky, all you get would just be some simple stomach ache that only lasts for hours. If not, well… just go to the hospital. Note that markets may also sell veggies/meat that may have been dipped into toxic chemicals, for profit.
A recent case is at the Adora Center, on Hoang Van Thu Street. Several people had shown symptoms of food poisoning. It is shocking to hear that, as I sometimes go past this majestic building here, not knowing its company’s shady reputation. Image is taken from theadora.vn
Traffic
Then, we have traffic issues. Due to the booming population, and with others transferring into HCMC and Hanoi for a hope of better jobs; streets are no longer capable compared to its population; and with the government’s limited visualization, this issue is nowhere to be fixed soon. Flooding streets are a thing too, and it happens after a heavy rain comes by. It has improved slightly compared to previous years, but you should concern about your vehicle, as it can knock out car engines too. These shouldn’t be a problem in small cities, such as Hue and Quang Ngai.
Flooding streets in HCMC after a rain, taken from infomoney.vn
Truong Chinh Street - one of the main streets leading to the city center and Tan Son Nhat Airport, in the morning.
And finally, the educational level of Vietnamese
Asians are good as school, and many Vietnamese students excel in school subjects. However, coming to the “Civil Education” side, the Vietnamese still has rooms for improvement. We have people robbing, littering, not lining up properly, driving terribly like if there were no rules, and such things like that. The education program is a part to blame, as it only focuses on academic skills, not social skills. People know if you don’t have good social skills, it’d be a problem to worry about. The lack of that also leads to certain problems that the country and its citizens will have to find a solution for.
I’d like to tell more, but since I don’t have much time to spend, I’ll have to end this here. Hopefully, after reading this, you will make out your opinion if life here is good or not.