At its best, Vietjet is a bare-bones but enjoyable experience. You can buy an extremely cheap ticket, and Vietjet's website makes it easy to book your flight and check-in online. You'll end up paying more than what you originally hoped for if you have any sort of bag or want to buy a coffee, but these add-ons aren't too expensive.
If I had a connecting flight or an important meeting, I'm not sure if I would trust Vietjet to get me there on time. And I'm still slightly offended by the $1 meal voucher, not to mention the mixed messages in its bikini-clad flight attendant marketing.
But, if you have a flexible schedule and you want a slightly quirky, super-cheap flight in Vietnam, Vietjet is a good pick. Hopefully you like Fiona Fung's "Proud of You" and Michael Jackson's "Heal the World," because you'll be hearing a lot of them.