I found the Farmstay in Phong Nha wonderful but almost too organised. The Farmstay and its owners seem to have played a huge part in opening up this area to western tourists and that is of course bringing lots of employment opportunities to the local people, which the Farmstay is keen to point out, there prices are really high compared to the rest of Vietnam. You really are in the middle of nowhere and so you are limited to booking everything you want to and buying all your food from Farmstay. They do it so well though and there are so many options from hiring a bike or motorbike, and they provide maps of the area with suggested places to visit to lots of one day tours and multi day tracks.
I met lots of fascinating people here including some of the first 6 tourists to be taken into Hang Son Doong cave. This is the biggest known cave in the world which was only discoverd last year by Howard Limbert from the British Caveing Assisiation who I also met. They had just returned from their 6 day tour which allegedly costs $3K per tourist. Book now as only 84 tourists a year will get to go. It was amazing to hear descriptions of the cave first hand, even from the photos you cannot really understand how huge it is. 
