Visa was easy, needed a letter that my travel agent arranged (very good guy btw located in Hanoi), paid $25 in cash at Hanoi airport (another $2 if you forget a photo) - funny note, they will only take USD. Took about 5 minutes.
Spent the first few nights on the beach - unbelievable. 20-30 miles of beach, almost no one on it, flawless sand, gentle surf.... spectacular. Ocean view 4-5 star hotel for under $100 a night (breakfast inclusive).
The only countryside I hit (other than the drive from Hoi An (about 30k south of Da Nang) to Hue - took about 3 hours) was Halong Bay - not to be missed, spent a night on the boat.
I'll go back in the next couple of years and do the Mekong Delta and then the area to the North West of Hanoi (and a few days in Hanoi).
I've spent quite a bit of time in Asia and love it, until this trip Thailand was my favorite spot - Vietnam just knocked it off the top spot.
If you want any specifics please feel free to PM me, a great experience I think many would enjoy.
OTB
PS. some web photos (not mine) of the sites I visited:
Halong Bay:
http://img6.travelblog.org/Photos/105101/382214/f/3575447-Junk-Boats-in-Halong-Bay-0.jpg
Hue:
http://media-cdn.tripadvisor.com/media/photo-s/01/19/26/57/hue-citadel.jpg
Hoi An:
http://www.asia-pictures.net/vietnam/images/collages maps/Hoi An photo collage.jpg
Hanoi:
http://www.hanoi-ultimate.com/pics/hanoi_str.jpg