I'm staying at the Hilton Hanoi Opera right now. One way flight from Saigon was USD $97, far better than the price quoted me back home. Thanks to all the FTers who guided me appropriately!
The hotel is very nice: surprising that it's one of two international Hiltons which will be downgraded come June 1 (Level 3 to Level 2).
In any case, I cant imagine a plane ticket from Hanoi to Danang is going to be much cheaper than $45, so if you can book and pay for it now, you'll save spending your time in the airline's ticket office.
Cheers.
Don in Hanoi