Vietnam is looking into being the first Asian country to recognise gay marriage, I assume you know this.
Can't add much to what Kenny said, except a violent disagreement about Hanoi. It makes Bangkok look like a pastoral idyll.
Hoi An, great, buy a suit, buy two, everyone (except me) does. Also has the most wonderful South China Sea beach...but not the main one. There's an out of town beach we had all to ourselves. Except the inevitable hawker.
You will leave Vietnam with the words "buy something" ringing in your ears.
I would probably have hated HCM (Saigon) if it were not for previously experiencing Hanoi. The two are the very definition of the phrase chalk and cheese. You'll see what I mean. Hanoi is enough to put the staunchest commie (me) off communism. Spent six months going round the world, S America, Aus, SE Asia, and Hanoi was the only place we went where we were prevented from going places. The army/state own the central square and you aren't allowed in. Which can involve massive detours if trying to get to the other side of the city.
Did I tell you Hanoi was shit btw?
How long you going for? I was there for three weeks and for me that was plenty long enough. I was in Laos for a month and that was far too short (going back next year).
We took night buses in Vietnam to save a nights accommodation. They have beds and with your Valium you will be able to sleep and thus miss all the near accidents your driver has.
Bit stoned, I'll stop rambling now.