Grab is fine in HCMC, and Hanoi. Even works well in parts of Cambodia now eg Sihanoukville and Phnom Penh. Used it regularly to/from the airports and around town. Never had a problem. Fares are always very reasonable and as quoted during the booking process.Grab is quite good, ive used it in the Philippines, Malaysia, Thailand and Vietnam. HCMC was a bit of a struggle though..... Others all OK. its just become one of the standard forms of travel now.
Even have a BEAT account in greece.