Have also used these guys a few times. Initially 5 stars, but the last few times I've had to chase down the confirmation - including calling from the Philippines last time out - hence the 4 stars. Overall though reliable and usually the drivers are polite and helpful. I have no problem recommending them, they speak English and (usually) reply to both email and text messages as needed.
I am so much impressive with this company. My flight was delayed for 2 hours and when i arrived at the exit gate of the airport terminal the driver was till there with my name. Easy to book, and very honest service. The transfer back to the airport from my hanoi hotel down town was also hassle free. Recommend it
Noibai Airport Taxi - Best Hanoi airport Taxi firm of 2012- Voted by its customers.
Noibai Airport Company is run and managed by Vietnam Backpacker Tour Co.,Ltd
Best Hanoi Taxi 2012
Tripadvisor and google users voted as reliable taxi firm in Hanoi