I'll be traveling in Vietnam in mid November. I'd like some feedback about the itinerary below. Of particular interest to me is whether the itinerary is realistic given travel times; I'm using estimates for travel times based on my Moon book, so recent first hand experience would be helpful.
Day 1) Fly into Saigon
Day 2) Saigon
Day 3) Mekong Delta tour
Day 4) Fly to Hanoi via daily flight
Day 4 - 6) Hanoi
Day 7) Depart Hanoi for Halong Bay via train to Bai Chay (~5 hrs)
Day 8) Halong Bay
Day 9) Depart Halong Bay back to Hanoi via train (~5 hrs); from Hanoi take the train to Lao Cai (~11 hrs); minibus from Lao Cai to Sapa
Day 10) Sapa
Day 11) Depart Sapa for Hanoi: minibus from Sapa to Lao Cai; train from Lao Cai to Hanoi (~11 hrs)
Day 12) Depart Hanoi for Angkor Wat via daily flight to Siem Reap
Day 13 - 14) Angkor Wat
Day 15) Depart Angkor Wat to Hanoi and Home
Any thoughts?

There is no train between Hanoi and Ha Long or Bai Chay. Many people take a tour to Ha Long bay (2-3 days). See post #98 in FAQ Vietnam about it. You can take a night train from Hanoi to Lao Cai, arrive in Lao Cai in early morning, take a bus to Sapa (30km). Also, if you re-enter Vietnam you will need a visa, or you must have a multi-entry visa.
As the direct flight between Hanoi and Siem Reap is expensive, about US$200 one way, I suggest you visit the Angkor while you are in southern Vietnam. Take a bus from SG to PP or Siem Reap, visit Angkor then fly to Hanoi. That way you will save one way flight HN - SR.

hongha -- my Moon book too says there is a train from Hanoi to Haiphong:
"4 trains leave daily from Hanoi to Haiphong, taking 2-2.5 hours for the trip..."
then --
"take the 10:00 train from Hanoi, arriving at Haiphong at 12:30, and giving you an hour to connect with the 13:30 ferry to Cat Ba Town."
Is this no longer true?
I'm considering a similar leg on my trip to Vietnam so thought I'd piggyback on this thread for clarification.
Thanks!
There are hydrofoil (fast) and ferry (slow) to Cat Ba from Hai Phong, but this way you will not enjoy the landscape of Ha Long bay. The tourist bus on organize tour goes from Hanoi to Ha Long town, you will have lunch and then cruise on the bay to Cat Ba island. If you go independently, you can take a local bus from Hanoi to Ha Long town at Gia Lam bus station, but problem is you will have to hire a boat in Ha Long bay or find someone to share the boat.
Sorry, regarding #4, I'm not sure if there is slow ferry between Hai Phong and Cat Ba or not, as I used hydrofoil. I guess Opera can help as she may know it.
Re: Itinerary
It looks a little cramped, a lot of travel and not much time at places.
HCMC warrants more than one day.
Personally, I love Vietnam and prefer to travel slowly. Most of Vietnam is about the atmosphere and ambience of the places and the people. Take it more slowly, the chances are that if you enjoy Vn, you will want to return anyway.
Whatever you choose, enjoy.

I'll have to agree with the last guy, ae123456, and say that you're moving around too much for such a short visit. If it were I, I would start in the North and end in HCMC. I would skip Cambodia for another trip entirely, and give that day to just exploring/shopping/photographing the Old Quarter of Hanoi (I'm a people watcher also!)
John