I bought this book as it was newer than the Lonley Plant version and so hopefully more helpful. In a way it was as it was indeed more up to date, had better info on hostels and restaurants etc... However, given the choice again i would choose the lonely planet for the following reasons.
1. the maps in the rough guide are sparse and fairly unhelpful. lonely planets versions are a lot clearer and easier to work with.
2. inaccurate information is littered through the book, more so in my opinion than the lp versions. things from buses, opening times, terrible reviews of hostels and even things like typos and incorrect page numbering.
3. the layout of the book is confusing and inconsistent. in one section you will have travel info at the start of the town and in the next it will be at the back.
Given all this, its still not a terrible book and we managed to travel around the area with no problems. It does lay out the highlights of each country, give a good synopsis and provide enough info to say hello (hola). On a side note, in the end we gave up on hostels in the book altogether and just used the internet as its more upto date, less biased and generally more helpful.