I make regular trips to Vietnam and I've used both the Rough Guide and Lonely Planet. Having seen the two latest editions, page by page, Lonely Planet is, simply, better. LP provides far more detail, more maps (all of which are much more user friendly and accurate), is loaded with contemporary information (NGOs, motor-biking etc), has better photographs, good illustrations, and entertaining side-bars. The book introduces us to the personalities and characters who run guest houses, restaurants, bars, boutiques, and so forth, and it really makes you feel like a local. The "reader from France" seems to have a personal animus against the writers and Lonely Planet. But otherwise, what could be the problem? I found this guide well researched, consistently useful, and fun to read - that's what I want when I'm on the road.