My wife and I just returned from a trip to Spain. I have used the Rough Guides in the past, and between the reviews of others as well as my personal experience, felt it was the guide book to take with us. After spending two weeks with it, it served us well and I would recommend it. We also took a slightly older (2007) Fodor's book which someone lent us, and were thus able to compare. The RG was the winner.
Older versions of their books were highly geared to backpackers and travelers with low budgets. RG has done a good job of covering a wider swath of the traveling public, and we found an excellent selection of both budget and higher end places for lodging and dining. A few times we had no idea of where to stay or dine, and their recommendations were spot on.
From the touring standpoint, I found their recommendations had a tendency towards hyperbole. For example, I found a "not-to-be-missed" sight could indeed easily be bypassed, and we could have saved the time and trouble. That happened on multiple occasions. The "best example of Mozarabic architecture" would likely enthrall an enthusiast, but my reaction was a tad more muted. The RG's orientation is for the traveler who is interested in or able to focus on an area for a longer period of time, as opposed to Fodor, who might suggest hitting one or two major sights and then hit the road. Our goal and method of travel is somewhere in between, so having the balance of the detail in RG with the opinion of Fodor in counterbalance was helpful. Having two books to carry, especially the thick RG, was viewed as an opportunity for exercise, not a burden.
One area that I must scold RG for is their choice of print font size and printing colors. My eyes are not what they were, and even in daylight we sometimes found it difficult to read. Section titles are mysteriously printed in orange, making that information fade remarkably well into the page, thus even more challenging to read. The book is detailed, very well written, and lengthy; make no mistake. To keep it compact, the pages are thin. I like to highlight passages, and the highlighter bled right through the page.
It is a worthy travel companion.