I used Uber extensively this summer in both Hanoi and Ho Chi Minh City. Very easy to use and incredibly cheap. Drivers were always happy to pick up and drop off at hotels, downtown, airports, etc. Almost none of them spoke enough English to communicate with me, but it was not a problem because the Uber app allows you to put in the destination and the drivers took me where I wanted to go. I found that it worked well to request the Uber and then immediately send the driver a text message advising the exact location (i.e. "Pick up at Sheraton Hotel") since the phone's GPS signal can be wonky.

I saw a lot of sad taxi dispatchers when I stepped to the curb and waited for my Uber. But the hotel front desk and bell staff actually said Uber was safer because the drivers are all vetted and background-checked, whereas the taxi drivers are not.