We went with Lindblad/National Geographic. We had booked an Antarctic cruise for this past winter and then later changed our minds. Our rather substantial deposit was nonrefundable but could be applied to another trip within a certain period of time -- thus we didn't do a lot of research on alternative vendors. This wasn't an inexpensive option, but we happened to catch a good sale last fall, in addition to using the deposit. Not our typical method of travel, but it exceeded our pretty high expectations.

How did you get from Phong Na to Ninh Bihn? Did you use a private driver? thanks

Plambers, we asked our hotel to arrange a driver for us. It was easy to do. And there are buses in town that head in that direction if you want that option.